Step 1: Put the boxes together
The first step is to put the two boxes together. Simply lay one of the boxes on the side of the other box and glue together. I used the blue tape to hold the boxes together while they dried.
The boxes I used had handle holes, so I added some cardboard to the sides and the inside. This covered the holes as well as added strength.
I also added a thick piece of cardboard between the two boxes and on the top for strength.