I saw this idea on the cricut message boards and figured I'd give it a try with my own twist.  I started with an 8.5 by 11 sheet of paper and cut it down to the size of the notebook lengthwise.  I then scored the sides to wrap around the notebook.  On the one I saw they used a piece of ribbon to keep the cover closed.  I didn't really like that idea so I decided to use magnets.