"Longies" are wool pants used as diaper covers. That's right, you put them over a cloth-diapered butt. Wool is incredibly absorbent and makes an excellent diaper cover.
The favored way of making them is to knit them, but I can't knit, and I have never found a crochet longies pattern that made a good fit. Buying them is cost prohibitive, and for good reason - 100% wool yarn is not cheap, and it is time intensive to make them.
So, what's a cloth diapering mama to do?
Sew them from a thrift store sweater.
I bought a sweater at Value Village for $4.00 - normally $6.99, but when I donated a small box of items, I got a $3.00-off coupon in exchange.
I made my 4 year old son's longies with the sweater sleaves. You just take a pair of pants that fit, fold them in half, and line them up on a sleave with the bottom of the pants lining up with the cuff. You cut from the crotch up to the top and over, leaving 1/4-1/2 inch for a seam on the side and 1-inch for a seam on the top (to leave room for elastic).
After you cut two sides, turn one inside out and place the other one inside it, so right sides will be facing inside. Pin, and sew the side and crotch area (don't sew the top!).
I did it once with a straight stitch and then again with a zig zag.
The next pictures didn't turn out, but once you sew the crotch, you turn the pants out and fold the top over an inch to make a casing for the elastic. Voila! I always try the pants on with the elastic just safety-pinned together to make sure it won't be too loose.
These are Deirdre's longies:
I used the front and back of the sweater for hers, with a Butterick pattern I have. They are baggier, and have a bigger backside than front area, which she needs because Connor will usually get up at night and only needs a fitted diaper "just in case." Deirdre needs lots of doublers at night.