Design ideas for a platform to lower camper onto...

If you need a visual on the concept of the plywood X's, take your hands and make the Vulcan salute with both hands. That's make a V with your ring and middle finger on one side, ring and pinky on the other.

Now take the two Vulcan salutes, point the open V's toward each other, and jam them together so they interlock. Now cut off your hands at the wrists (in your imagination, or literally, your choice) and pretend they're sheets of plywood.