OK. They're done. I said that I would post pics, but there's really nothing to see.
All I did was fuse a 4" X 6" piece of interfacing to a 4 1/2" X 6 1/2" piece of plain muslin. I made 12 of them.
Now, when I finish my next quilt, I'll have NO excuse not to finish it up and sew it on.