I bought a felted (i.e. shrunken) sweater at a yard sale last summer for 50¢ planning on using it to make Will some soakers. I decided I'd better make it since the arms are quite small/thin!
Here are the steps I used....
Cut off the arms and figure out the angle for the crotch seam. I didn't have enough width for the right angle, so I opted to add a gusset in the crotch.
I traced one half of Will's green longies before I sewed them up to use as a pattern. It is folded in half since the arms are 2 layers!
Sew the crotch gusset.
Put one leg inside the other with right sides together and sew front and back seams using a ¼" seam.
I stretched the wool as I sewed.
Zig-zag the seams.
Sew a casing at the top for elastic.
Thread elastic through the casing and sew ends together.
William modeling them.
Close up view.
Back view (same as the front!).