The manufacturer recommends placing the shed on a flat structure such as a wooden foundation made of treated 2 x 4’s and OSB board that you can pick up from your local home improvement store. The instructions show just how to build it and what materials are needed. The other recommendation is a concrete slab. The concrete slab is more pricey to erect. Some customers put it on cinder blocks, pea gravel, or other flat structures. The important thing is to make sure it is flat and drains well. If it isn’t flat you may run into issues with your doors closing properly.