It's really easy to do, doesn't require any pattern, and can be made in under an hour.
Step 1: What You Need
One large chunk of fleece, about 3 feet by a little over 1 foot (It was a scrap I found around the house)
One shoelace (I'm sure you can find something to do with the other one on Instructables somewhere)
A sewing machine
Step 2: Trim
Step 3: Pin
On the right side, pin about one foot up the side, then start arching deeper into the fabric, until you're 5 or so inches in. You want to do this in a curve.