Below is a similar project you may enjoy. It's a great way to use and recycle your favorite holiday greeting cards. These cardboard boxes can be any size, depending on the size of the cards that are used.
Photographs work well, too.
You'll need an X-Acto knife also. Open up the card and cut straight down the fold line of the card. This allows the bottom of the box to be smaller than the top. With a pencil, mark off 1-inch on each side. An easy way to do this without measuring each time is to cut a 1-inch cardboard strip and use that as a guide against the edges of the card.