Mini Greenhouse made from Hay or Straw Bales. This is a great idea and the hay has multiple purposes once you decide you don't need the greenhouse any more. You could also use plastic sheets if you have no glass windows or doors lying around!
Pressure-treated lumber laid on a bed of gravel gives you a fast, easy foundation that will last for decades, fill the wood foundation with gravel and lay cement pavers, just like for a paver patio. A paver floor allows water to drain through