I used a small amount of beautiful striped fabric that my mom wasn't going to use, and had to cut the fabric in interesting ways just to get it to fit on there correctly. Turns out it is a little too big anyway, so I didn't really need to do all of that brainstorming on how to get it to fit on the fabric. I used an old sheet to make the straps and elastic casing. The pattern is a little too full around the middle for my liking, but I think it is just because I didn't use a drapey fabric. I took in the sides and like it better.

cotton, bedsheet for straps and casing