Usually people use an egg crate frame so you don't need as much rock... since you really won't have a base.
You can do it by basically making a "stadium seating" type arrangement out of PVC and egg crate. I would use PVC for the frame, and zip tie the egg crate to the PVC for the "seats" or flat portions where the rock would sit. This way livestock can still move underneath and behind the structure.
There's a TOTM where the guy did it, I'll have to try and dig it up.