I started with a pallet box thingie from my neighbors burn pile. I filled in the gaps with scrap wood, then put a door on some spare hinges I had laying around. on top I used some spare rubber roofing that was laying around.
Great job! Love the use of recycled materials. I just made a pallet compost system the other day that is 12x4 (three 4x4 bins) and it cost almost nothing.