4" Zipper (JoAnn's, Fabric Stores)
Old Pair of Jeans (or whatever)
Sewing Machine (or you can sew them by hand)
You need a piece of material 5 1/2 x 9 inches this allows for a 1/4 inch seam using a 4" zipper.
Before I cut them up I took a picture in my old jeans as inspiration for the days when I don't want to exercise or want to eat something I probably shouldn't.