|Photo from Happy Together|
There's a free downloadable pattern, and the only other things you need -- other than a sewing machine and basic sewing supplies -- are fabric and elastic. Very small amounts of fabric will be needed, so this would be a great way to use up some of your scraps.
The tutorial looks clear and the process simple. I'm thinking I'll make a bunch of these for the girls on my list. Summer is a great time to make fun little projects like this!