Ladybug 1938, when I made pillows at the drapery shop, I always used zippers and the case was cut exactly to the pillow mold size. If you are making your own muslin ones , stuff it full but not tight. Sew the stuffing in and then make the cases to fit. Attach zipper to bottom. If you have trouble inserting mold then wrap a flat piece plastic around it and shove them in the casing and pull plastic out and zip shut. It worked every time for me and my crew. It took all the struggle out of it. Shirley Anne