Knocked this up in just under an hour. I had most of it lying around the house so it was totally free and fun. Learnt a bit of Algebra as well. This is how to make the basic shape:
1. Draw and cut desired circle size.
2. Find the circumference by measuring across the circle (the diameter) and times it by Pie (3.14). BOOOOOM. You have your circumference, yo.
3. Cut a rectangle piece of Leatherette to the specifications you cleverly worked out above and sew the two ends together. You should have a piece of material that resembles a sleeve.
4. Pin your circle bottom to what ever end you feel like and sew.
This is in no way made especially well, I might hasten to add.