Unzip the side with the zipper. Take the 19 x 19 bottom side, line up the edges, and sew along the stitch line from the piping. To make the pillow insert, cut all of the same pieces, except I did ...

If you're using a zipper, attach it to the open side. Finally, insert the foam into the fabric cover ... pillow that can attach to the wedge, as shown in a YouTube tutorial posted by Sewing ...