1. With wrong sides inside, fold solid sage green 16-1/2x20-1/2" rectangles in half to form two double-thick 16-1/2x10-1/4" pieces. Overlap folded edges by about 4" to make a 16-1/2" square (Pillow Back Assembly Diagram). Stitch around entire square to make pillow back. (The double thickness makes the pillow back more stable.)
2. Layer pillow top and pillow back with right sides together. Stitch around all edges. Turn right side out and press to make pillow cover. Insert pillow form through opening in back to complete pillow.