This was one of those ideas I saw in a magazine a while back and thought, "I have to try that."
You start with a placemat.
I bought this one from Target for $2.99. You just need to make sure that it's double sided (instead of just a piece of fabric that's hemmed all the way around).
Grab your seam ripper and pull out the hem on one side of your placemat. I chose the right side.
Once you've ripped out that seam, you will need to rip through the seam holding the two pieces together just inside.
I just ripped a few inches open - enough space to stuff with my filling.
Next, grab your polyfill (or even the filling from an old pillow you don't like anymore) and start stuffing.
When it's full enough, press the open end together and pin along the edge. You don't have to be quite as OCD about this step as I was. :)
Now sew a straight line near the very edge that matches the other hems and you've got a new pillow! A pillow that was, in its former life, a placemat.
Who would even know?!