I was part of the team that helped make this Instructable for a class project. You don't have to fold the pages, but then you will need to make some sort of groves at the spine so that the glue has more surface area to seep into, making a stronger bond. Folding the pages into signatures (I didn't actually stack the pages into signatures, i treated each folded page as a signature) creates groves at the spine to allow the glue to seep in between the pages. This was just an attempt to quickly make a cheap class notebook. I will make another Instructable on how to make a higher quality book that can be used for a journal or something of that sort, which will have sown/glued signatures with a hardcover.