We use prefold diapers and covers over at our house. I find that I like them a lot better than any other cloth diaper both for use and cost. I've mastered quite a few folding techniques and the covers do a good job keeping the cotton in, but with a boy, getting that just-right-fit is difficult.
Especially, if they're like Max and like to "help" you put the diaper on by taking it off or try and run away all together.
I've been working on this for a little bit, the nice thing is that it doesn't have to be perfect since no one will really see it and if they do, chances are they're poo-stained anyway. Who's going to look closely at sewing lines at that point?
Take your flat diaper, I use unbleached indian cotton, and lay it flat. Measure out approx 5" on one side and 3.5" on the other. The five inches will be the "back" and the 3.5 the "front" when you put the diaper on. Mark these places and draw a semi-circle connecting them like this:
Sew a tack stitch along the line you made. Cut off the semi-circles along the sitch line without cutting the stitches.
Cut off the stitching along one end and "open" the diaper so the outside is now inside ripping the inside seams apart. You might have to work the folds of the middle section a bit. Sew it all the way around the edges and then turn it back right side out.
You may have to sew down the side where the fold of the diaper meets. Sew a top stitch around the whole diaper and on the end you opened sew it closed with a tight zig zag.