I have a 16' round easy set pool. The type with the inflatable ring at the top. We have set it up twice on what we thought was level ground, only to discover it wasn't. I tried so many methods that I am just confused. What's the best way to find out if it is level? Then, what is the simplest way to get it level. Is there a special tool? Or is it just some mysterious trade secret no one wants to share.