Cut long-side flaps from the bottom of second box. Cut one short-side flap so that when the box is assembled and stacked on the bottom box, the holes will line up. Secure the flaps to the side of the box with a line of hot glue. Hold flaps in place until glue is set. Coat the top of the bottom box with a generous layer of hot glue. Position the bottom of the top box over it, and hold in place until the glue is set. Use one of the reserved short side flaps and coat one side of it with a generous layer of hot glue. Place it, glue-coated-side down, as pictured, on the "floor" of the top box for reinforcement.