I found this really cute fabric at Joann, and bought what I thought was enough for a standard-sized pillowcase. I knew I was going to the opening edge in a contrasting fabric, like these from Made.
Turns out I did not get enough fabric, so it's a little short all the way around. Luckily we had an IKEA pillow form, and since everything in the store is tiny, it worked out okay.
Now I want more of this fabric for a sheet to match! (These are for the girl, of course.)