Cut 2 rectangles measuring 64x36 inches from fabric.
Sew edges using a 1-inch seam allowance, leaving open a 36-inch end.
On one open end, sew Velcro to the wrong side of the fabric.
Sew the other half of the Velcro to the correct side of the fabric on the other open end.
Turn inside out.
Insert 2 pieces of foam, one right after the other. Close the Velcro.
Chair can be sewn closed instead of using Velcro, but with Velcro, the cover can be removed and washed.
Cut 4 rectangles measuring 64x38-inches from fabric.
Place 2 rectangles, right side of fabric together, and sew edges using a 1-inch seam allowance, leaving open one 38-inch end. Repeat for second set of rectangles. You now have a sofa back and sofa seat not yet joined.
Select a rectangle: On one side of the open end, sew Velcro to wrong side of the fabric. Sew the other half of Velcro to the correct side of the fabric on the other side of open end. Repeat for second rectangle.
Turn both rectangles inside out.
Matching the rectangle ends with the Velcro openings. Place one 64-inch long rectangle side, 1-inch on top of the right side of the fabric on top of the other rectangle. Pin the 2 rectangles together. The sofa back and seat should be pinned side by side.
Using the widest zigzag function on your machine, zigzag the entire length of 64-inch rectangles, joining the 2 rectangles side-by-side. Repeat.
Insert 2 pieces of foam, one right after the other, into a rectangle. Repeat for other rectangle. Close the Velcro.
Sofa can be sewn closed instead of Velcro, but with Velcro, the cover can be removed and washed.