I like to have something under my desk to put my feet up on, and I recently moved the file boxes I had down there (they were getting kind of dirty from being used as foot stools, so I made room for them on my bookshelf), so I decided to make myself a fabric ottoman cube to use instead.
I used a loosely woven home dec fabric, and underlined it with a grey sheet. I cut 6 squares, 18″x18″ out of each fabric, and sewed them into a cube, using a 1/2″ seam allowance. I inserted a zipper along one of the seams for easy stuffing. And then I used a bunch of fabric that was leftover from sewing bags a few years ago to stuff it.
It ended up being a little larger than I had anticipated, but it does fit under my desk and it works well for putting my feet up!