I cant think of the name of the product that was used on mine. It was a foam bead mixed with cement that the installer put down, brushed out flat, formed a cove, wetted, and put the liner in. The product hardned and made a nice bottom that felt like foam but was formable. It has a nice spring to it and you dont leave foot prints. He said that small rocks were not a problem like sand. I cant rember if he said anything about grass. I am on a red clay hill and he had to scrape 20 inches on one side so grass was not a issue. I didnt get wall foam.
If you want I will call the pool store and get the product name.
Steve