humph... I thought it was no problem!!!
I just bought some hemp from Kidsinthegarden, prewashed it twice (put it in with whatever) and then folded and cut to size and sewed with zig-zag stitch. The ends tend to roll when you have prepped the fabric, but to me it was not a big deal at all. Yes, my edges are a bit raggedy compared to ones that have been serged, but the thing goes inside a diaper, so I really see no need for perfection.
that said, hemp isn't very cheap, so you are only going to be saving much money if you are doing a lot of inserts.