Place the dust cover fabric over the seat base and cut around the edges of the set to get the exact dimensions. This piece will be hidden under the foam and fabric, so don't worry if the edges are a little jagged. A dust cover will help to prevent the cushion from sagging down into the seat base. Place the dust cover onto the seat base and staple around the edges to secure it to the seat base. Make sure that the fabric is taut. You may want to place 1 staple at the center of each side to start and then work outwards on each side, pulling the fabric as you go. Place the seat frame directly onto the foam. Trace around it using a pen or marker. Then, use a serrated knife or an electric knife to cut out the foam using the lines you traced onto it as guides. A bread knife or turkey carving electric knife work well for cutting foam padding. After you have the foam cut out, place it onto the seat frame so that the edges of the foam and seat are lined up. Place the foam directly on the batting and the seat frame on top of the foam. Make sure that the foam and seat are centered on the batting. Don't worry about the dimensions of the batting. Use a large piece and cut what you need after you have the seat and foam in position. The edges of the batting need to go up and over the edges of the back of the seat by 2 inches (5.1cm) on all sides. Check to ensure that you can wrap the batting around by 2 inches (5.1cm) on all sides and then cut the batting to these dimension. Mark the batting to indicate where to cut it or cut it while it is wrapped over the edge of the seat. Staple the center of each edge of the batting first, and then continue stapling along the edges on each side. Pull the padding taut along each edge as you staple it. Work from the center staple out towards a corner of the seat and repeat this on both sides of the staple. Then, do the same thing for each of the other sides. Gather the excess fabric at 1 corner of the seat, and then fold it over at the corner. Staple in the center of the fold to secure the fabric at the corner of the seat. If there is still some extra fabric, fold it again and place another staple over the fold to secure it. Repeat this for each corner of the chair. Once the batting is secured to the seat, cut the excess to reduce the bulk and prevent any hanging fabric. Cut about 1 inch (2.5cm) from the staples all around the inside of the seat. Don't cut the batting too close to the staples or it may come loose.

Summary:
Cut a piece of the dust cover fabric to the dimensions of the seat. Staple the dust cover to the top of the seat. Cut 2in (5.1cm) thick foam padding to the dimensions of the seat. Place the foam padding and seat onto a piece of batting. Cut the batting 2in (5.1cm) past the seat's edges. Staple the batting to the center of the seat and then work outwards. Fold the batting at the corner and staple to secure it. Cut the excess batting 1 inch (2.5cm) from the staples.