Find free pallets from Craigslist. If not available, you can purchase them locally for very little money. When searching through the pallet stack, look for the pallets with the most usable wood. The length of the slats is ~ 3 feet. The thickness varies from ½ to ¾ thick. The width of the slats can vary from 2.5 to 6 inches.
Breaking the pallets apart takes a decent amount of work. Use a jig or circular saw to cut the ends. Pry the wood from the center support. This should give you 8 to 14 boards per pallet. Remove nails from slats.
Before you start cutting, determine the best pieces to get the desired width (see drawing). I had multiple long pieces with cracks and/or damage down one side. I was able to cut the damage off and still have usable pieces.
After cutting the pieces, sand them with course sandpaper to remove rough spots or major staining/paint…unless that is your desired look.
Assemble top frame (nail & glue)
Assemble bottom platform (nail & glue).
Ready for next step
Attach the sides to the top frame and bottom platform (nail & glue).
Attach the side trim to the upper sides (nail & glue). Attach the top trim (nail & glue).
Finish as desired. Version shown is finished with red oak stain and coated with an outdoor urethane.
Finished project - project done in the winter (no plants yet)!