First, map out where you want the stenciled designs to go. Use a light-colored washable marker to make small marks so you know where to place the stencil each time. Place one hand firmly on the stencil to make sure it doesn't move and hold the can about 4 inches (10cm) away from the carpet to spray in the design. Purchase pre-made stencils from craft stores or make your own out of cardboard or thin plastic materials. It's best to use just one stenciled design, but you can combine two different stencils if you lay them out in a thoughtful way. For instance, stick to a single celtic design to be spaced out evenly across the center of the carpet or around the edges. You can also use different floral stencils for a smart, unique look. Use painter's tape to act as a stencil. Lay it out in stripes, chevron patterns, triangles, or any other geometric shape you enjoy. Then, spray the areas around the tape, let the paint dry for 1 to 2 hours, and peel back the tape. Try cutting the tape into small squares and triangles and sticking them to the carpet to create your own geometric patterns. It may help to use a measuring tape to map out where you want to place the painter's tape for a symmetrical design. Create a classic border of stripes around the edges of the carpet with lines of painter's tape. Use a measuring tape to measure out where you want the border lines to go, then make small tick marks with a light-colored washable marker. Lay the tape according to the tick marks. The areas covered by tape will reveal the current color of the carpet. Hold up a piece of cardboard at a 45-degree angle next to the tape line to protect the inside section of the carpet from the paint. Blot the painter's tape or stencil with a rag to soak up any puddles of paint that may have collected on them. That way, when you peel away the tape or lift the stencil, the puddle won't drip onto the carpet and ruin your design. Pull up the tape or remove the stencil only after you're finished painting that area. Touch the painted area with your finger to make sure it's dry before moving on with a new color or before laying down more painter's tape. If your design requires adding more tape to previously painted areas, wait until those areas are completely dry. For instance, if you spray red spray paint over blue paint that isn't dry, you could end up with purple areas. Placing tape onto still-damp painted areas will compromise the consistency of the paint and, as a result, mess up your design. Use a paper towel to wipe up as much of the excess paint as possible, then douse a cloth with paint thinner and blot or rub the affected area until you don't see any traces of color. Mineral spirits or acetone can also be used to remove paint. Avoid stepping on the painted areas of the carpet for the next 8 to 10 hours or until it's completely dry. Depending on the climate and humidity of the area you live in, this could take up to 12 or even 24 hours.
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One-sentence summary -- Use a stencil to create curved, intricate designs. Lay down painter's tape in geometric patterns for a modern look. Apply stripes of painter's tape around the edges of the carpet to make a border. Use a rag to remove any puddled paint on the tape or stencils. Allow the paint to dry before adding a new color or more tape for the design. Use paint thinner to clean up your design or erase mistakes. Wait 8 to 10 hours until the rug is completely dry before walking on it.

Soapstone's texture resembles a dry bar of soap and is extremely malleable. It will easily form a shape with little force. Soapstone is so soft that you can carve it with harder rocks you find in your backyard; you can even use your fingernail to carve it. It also comes in many colors like grey, green, and black. Use soapstone if you are making a small sculpture that won't be easily damaged if you accidentally scratch or nudge it. You can find soapstone and other soft rocks at a local stone carving supplies stores. For example, in California there is a store called "Stone Sculptors Supplies" that sells soft stones for carving. Alternately, you can acquire your stones from a stone yard. Know, however, that these stones are typically used for construction purposes (building counter tops, for example) and may be harder than artistically provided stones. Know that some soapstone contains asbestos, which can cause lung cancer, asbestosis, and mesothelioma if inhaled. Alabaster comes in a wide range of colors and is available from many suppliers. Alabaster is best if you want a colorful, sturdy sculpture. It can come in variety of colors like white, grey, beige, orange, yellows, reds, and translucent. Although alabaster is generally harder than soapstone, it still carves easily. It is the ideal choice for new sculptors since it will still retain its shape without requiring specialized tools or strenuous effort. An alternative to alabaster is limestone, which carves easily and regularly but is not available in a wide range of colors (typical limestone comes in different shades of grey). Also, limestone can be difficult to sculpt if you get the wrong piece. Limestone is slightly harder and doesn't polish as well as alabaster. Carving these stones requires specialized tools like electric grinders and hammers. Granite and marble are usually sculpted in large quantities since they are most optimal for statues and other large items that require durability. Working with large slabs of hard stones requires very strenuous effort. Even experienced carvers can spend up to 80 hours working on a relatively simple piece. Carving is a subtractive process, not an additive one. Unlike adding more paint to a portrait, carving involves taking away stone to create the piece's shape. Limit your stone size to something you will finish in a relatively short time. This is especially important if you are trying your hand at sculpting for the first time and are unsure of whether you will enjoy the process. The suggested size of stone blocks for sculpting is 15-25 lbs. Blocks that are smaller than 15 lbs will break if carved with a hammer and chisel. Any larger, and completing your sculpture will take much longer than you desire. If you intend on using soapstone to sculpt a heart-shaped pendant, then you can most likely work with a block well under 15 lbs. Just remember that you will most likely have to use other, less accurate tools like harder rocks or a file to shape it. You will also have fewer chances to correct any mistakes you accidentally make during the carving process. Since you're working with natural materials, it won't be unusual to experience structural flaws. Finding a stone with few flaws will reduce the likelihood that your stone will break when carving. Cracks and fissures are sometimes easiest to see when the stone is wet. Use a spray bottle or sprinkle water over your stone. If you find any cracks, try to follow it to see where it ends. A crack that goes all the way around a stone is in danger of breaking during the carving process. Tap larger stone blocks with a hammer or the back of a chisel. If the block makes a "ringing" sound, there is a higher chance that your stone is solid in the area you are hitting it. If it gives off a dead "thud" and no ring, chances are there is a crack that is absorbing the energy of the tap. Ask an experienced carver or a store employee to help you find a sturdy stone to work with. If you are a beginner and do not have experience judging the integrity of a stone, acquire your stone from a stone carving supplier instead of a stone yard.
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One-sentence summary --
Choose soapstone if you are a beginner and have few tools for carving. Buy alabaster for the best combination of durability and malleability. Avoid very hard stones like granite and marble. Pick a slab of stone that is much larger than your intended sculpture. Inspect your stone for cracks and fissures.