The one shown is the one I made last year and was done with PUL and fleece. For that kind, I suggest sizing up on the body of the soaker but keeping the waistband and leg cuffs the size you actually need.
Cut out the soaker pattern you need.
Fold the edges (formerly the side seams) in one inch in the front, and 7/8" in the back. The wrong sides should be together when you do this so that you have a neat looking front. Stitch these down.
Fold the short edges of you waistband pieces in 1/2" with wrong sides together. Stitch these down. Then fold the long sides together (wrong sides together) and stitch the raw edges together with the raw edges of the soaker body, stretching the waistband to fit along the soaker. Do the same with your leg cuffs.
Once all of the pieces of your soaker are together, center your snaps in the waistband at the edge, center them in the leg cuffs at the edge, and center them in the sides of the soaker.
I know these instructions leave a lot to be desired, but I will try to get some pictures up soon.
Side-snapping soaker pattern