ReadyMade has an excellent guide on making real "lawn furniture," specifically a sodded sofa:
Before you begin, figure the dirt you need by multiplying the dimensions of the couch you plan to make (ours was 8' x 4' x 4', or 128 cubic feet). Next, put on some old clothes—things are going to get messy—and locate a suitable spot. Placement is key: There'll be no moving once you've begun. Clear the area of grass and weeds until you have a level swath of dirt, then use a stick to sketch the shape of the couch into the dirt with a stick…
