All the boxes are constructed with butt joints and wood glue. The wood glue was transferred to a small bottle with a fine tip to be able to accurately glue the 1/4 inch plywood. With this bottle, we were able to glue with very little squeeze out to clean up.
To keep the walls in place while they dried, we propped them in place with vintage seven-pound irons and weights.
We also used clamps where we could while parts dried.
To keep the boxes securely together, we cut angle iron to the height of the stacked boxes, then we glued this to the bottom box.