1) Cut the boards to the specs below or adjust to your space
2) Kreg Jig the cut boards along each of the sides (length wise and on the ends) for attaching and making a box.
3) Make 3 separate boxes, don't assemble until you move to location. I used 4x4 cedar posts in the corners of the base box to add stability. I used 2x2 pine in the front corners of boxes 2 and 3 for stability. Install these after the dirt has been added so you can hammer in as a stake, attach with screws on front and sides. I created 2 stakes for boxes 2 and 3 and added to the front to prevent bowing when the dirt is added.
1) (base) 70.5" L x 46 W x 4 cedar boards high
2) 70.5" L x 32 W x 2 cedar boards high
3) 70.5" L x 16 W x 2 cedar boards high