It is very simple. I just measured about 1/2 in extra on each side and then I just used my adhesive to tack it down. Just make sure your tag pulls out smoothly. This book was so fun to make. I basically left the book at home during our trip and just took the tags with a small clipboard that had a pen velcro to it. The tags fit neatly in a quart size ziplock. I wrote in pencil on the back of each tag for each character so I knew whose tag belong to whom.
If you have anymore questions don't hesitate to ask.