Still kind of confused as to what you are looking for. A "deck " is usually raised above the grass surface to create a smooth surface for leisure. This coud be built as a box type structure just resting on the ground or built on stilts to raise it further off the ground. you could cover the top of the frame with exterior grade plywood and cover this with fake grass. There are plenty of books at home depot, Lowes etc. about deck bulding, probably some at your library too. Do a little research and you can see what will suit your needs.