I propped it up by adding my gear/clothes under the mattress.
Today I found some wood in my garage like plywood, 2x4s, and 4x4s and I made a poor mans platform.
I want my head to be by the rear entertainment system. I found this area to be less cold and more comfortable than having my head by the rear barn door.
I carry my gear in container boxes, so I do have to unload them to make the entire back my sleeping bedroom.
Ideally, the Wood platform is 34x36, 2 36” 4x4s, and 2 10” 2x4s. My scrap wood came close.