Okay! Here's a FOE tutorial. For easy reference, I've listed some projects I have made using this handy fold over elastic. There are links in the various posts on where to buy it.
I hope you find it informative. It's about 8 minutes long. Sometimes when a bunch of people are trying to watch videos at once, you tube says it's no longer available—which is hogwash. Just come back later and try again. Here's the direct link, too.
And look what I found! A video tutorial on using FOE for diaper covers. There are a ton of sewing tutorials on you tube, including what appears to be a 17-part series (possibly more?) on sewing your own underwear. For real. I think it is only one pair (the pace is pretty slow going and the clips are really short, hence the high number of episodes) and combines all the crazy reasons I love the internet. It's incredibly rad, you'll know what I mean when you watch it.
*stick heads included. You can see their first appearance here.