It took about 15 minutes to do as the smaller areas take time as you only go through a few layers at a time, but it was easy and fun to make. I was worried that some of the choppy areas would make it look bad, but I think it gives it more character.
Download the diagram from
Print off, cut out the circle, then fold accordion style and cut out the gray parts with the X-Acto knife.
If you need further instruction on how to fold, there is a link to the tutorial: