This is what I did. Was getting a shed and they would have charged a lot for leveling the site. Mine was about 6 or 7 inches out of level, so I dug down a little, provided them with level blocks in the corners, and a pile of extra blocks to use. They said that was perfect and once they had the base framing set on the corners, wedged in the other blocks on the sides and down the center to prevent bounce. These were flat blocks, not the ones that have grooves for framing.