Will only had one wool soaker, so if I wanted him to wear a onesie, he had to wear plastic pants over his diaper. I dug out the remains of the felted sweater I used for his longies and set to work making him another pair.
I traced the soaker that he had and then added to the width since the sweater won't stretch as much.
I laid the pattern on the sweater. I left the extra ribbing at the top to use for a casing. I also used the side seam already in the sweater.
Here it is cut out.
I sewed the seams stretching the wool as I went.
Fold over the top of the ribbing and sew for a casing for the elastic.
Thread the elastic.
Here it is so far.
I tried it on William.
I tightened the elastic and sewed a hem on the legs.
Close up view.