Last week, my grandmother showed me this. I love the simplicity and the fact that it looks so cute! I'll tell you how to do it.
When you're done, you can use it for sticking in things like postcards or photos.
Start with a book you don't want any more (or buy it for a few cents in a charity shop). It cannot have more than 100 pages, or the hedgehog will be too 'round'. It makes it easier when it's a paperback.
Start with folding the pages in half. Then fold back the corners, as you can see on the picture.