I’m sorry this isn’t a full pattern, but Ravelry doesn’t seem to have a spot for things like this so they inadvertently deleted my first attempt to put it up here. Apparently it is okay after all so I hope you’ll find yet another buttonhole technique useful anyway.

If you know how to knit chains by doing a yarn over and passing the stitch on the right needle over it you can get by without using a crochet hook at all.

This is strongest, tidiest (from both sides!) best-behaved one-row buttonhole I’ve been able to devise. The instructions may look long and a little intimidating but once practiced a couple of times the buttonhole itself is very fast to do.