So I had a few blocks of cement block laying around from shelves that we made for the kids and some landscaping projects. I want to place a cement block at each corner of my structure. I am doing this because the ground is NOT level. The ground slopes downward towards the back of our property. I think this is good as rain SHOULD flow underneath the structure. I already had staked out the area with string; so I set a cement block at each corner just inside my string. I then took sown the string rectangle and spray painted around the cent blocks with a color of spray paint that would show up on my grass. I figured that when I dug this would keep me from being WAY off. That kind of worked.
The back corners of the structure are level and I do not need to dig. I took a 2x4x12 and placed it across the 2 cement blocks then I used a level to make sure. I am pretty sure that was a lucky break for me. i only had to dig in the other 2 locations in order to level the outside frame.
I just dug a little outside the spray paint and set the cement block in. I did not use any gravel or cement. I just dug and evened out the soil where I needed to and placed the block in the hole.
It took about 1 hour to dig in the 2 locations and actually get the blocks to create a level plane. I checked the opposite sides by placing a 2x4x12 corner to corner and using the level. I had to try a couple of times; but I got it.