If you want to make a cube that's 2 2 2in (5.1 5.1 5.1cm), use a pencil and a ruler to create a rectangle that's 8in (20cm) long and 2in (5.1cm) tall. For a cube of this size, your paper should be at least 8in 6in (20cm 15cm). Construction paper is best for this project because it's sturdy, but you can also use standard copy paper. If you want to make a cube that's a different size, start with a rectangle with a length-to-width ratio of 4:1. For instance, if you want to make a cube that measures 4 4 4in (10 10 10cm), draw a 16in 4in (41cm 10cm) rectangle to start. Starting on the far left side of the far-left box, draw 2 lines that angle in toward each other at about 45. The lines should be about 12in (1.3cm) long. Then, connect the angled lines with a straight vertical line to make your flap. You'll also need flaps on either side of the top box, a flap on the bottom of the box just below that, one on the bottom of the very bottom box, and a flap on the top and bottom of the far-right box. The only box that won't have a flap is the third box on your original rectangle. The very top and far-right boxes will have two flaps each, and the far-left, second-from-the-left, and bottom boxes will each have one flap. This will be 7 flaps total, and you'll use them to glue your cube together. Using a pair of scissors, carefully cut along only the outside lines of your template, including the flaps. Don't cut along the lines that divide the boxes from one another, or the lines between the flaps and the boxes. Your template should be 1 big piece when you're finished. If you accidentally make the wrong cut, either tape the template back together or draw a new one. Place a small line of glue on one of the flaps, then hold the flap tightly against the corresponding side for several seconds. Continue doing this until you've glued down all of the flaps, then leave the cube alone for several minutes to give it time to dry. You can use tape to fasten the flaps, if you prefer.

Summary:
Draw an 8in 2in (20.3cm 5.1cm) rectangle on a sheet of paper. Draw 7 parallelograms to create the flaps for your cube. Cut out the cube template. Add glue to each flap as you put the cube together.