I finally got around to making one of these. I'd been meaning to for a while, and yesterday I just sat down and made one. At first I had a little trouble assembling it (I wasn't actually looking at how other people had done it - I decided to wing it), so I made two smaller ones:
Of course, after I put them together, I figured out how I should have done it. So I took them apart, and sewed it back together into one.
I really should sew buttons on, but at the moment I don't have any that work well with it.