Place the bottom of the 8" deep pocket along the bottom of the backing piece. Gather to fit and stitch the pocket in to place, in the outside 1/4" edge. Line up the edges of the pocket with the edges of the backing, stitch up to the elastic casing but do not stitch the casing. Pull the elastic to make the pocket fit to the backing. DO NOT pull the elastic too tight. This will cause the backing piece to want to curl. Tack the elastic into place. Reinforce the stitching by stitching over the elastic a couple of times on the outside 1/4" edge.
For the middle pocket, Place the edges of the pocket 1/2" above the ends of the bottom pocket. Gather the pocket bottom to fit the backing. Place the bottom edge inside a folded piece of grosgrain ribbon. Pin the pocket bottom into place and stitch the pocket to the backing. Make a row of top stitching on the upper and the lower edge of the grosgrain ribbon to add strength to the bottom of the pocket.
For the top pocket, line the side edges up with the backing piece. Gather the bottom of the pocket to fit and repeat the construction of the middle pocket.