Mom says this works better with an 11x17 sheet, but we had 8.5x11 so that's what's in these photos. It's okay to use a scrap paper that's been printed on one side, your blank side will be the only one showing.
Start by folding your paper in half down the middle.
Then fold again lengthwise
Then fold in half again so now it's in eighths
Now unfold until you're back to the one fold in half:
Cut from the center fold to the 1/4 fold, right in the middle:
Unfold only the top layer, along your fold line:
Now fold width-wise back to 1/4:
Fold in half again so you're back down to the 1/8 size:
Start your book! It should stay together very nicely.