To build one of these you have to plan, procure all the parts, and then the easy part, do the assembly. I procured an old trailer from a friend, it was used to transport ATVs. I won’t bore you with the grinding rust and under coating the whole frame. I then applied a waterproof membrane and screwed the 2X4 wood frame(also undercoated) to the steel frame with some stainless steel self drilling and self tapping screws I bought at of garage sale. A whole bucket of assorted sizes for $5.00. I placed 1.5″ solid pink insulation in between the framing.