We started camping with truck campers in the late '60s and '70s. Back then COE camp grounds on our many COE lakes were a dirt road winding between the trees with picnic tables scattered around. Nothing was level or even flat.
To get level we may have to dig down one side, or end down, and block up the other end or side maybe a foot. No gravel or concrete or asphalt campsites or pads.
So I still carry a big assortment of blocks/ramps/pads for any event.
My ramps and blocks were made from cedar garage door header drop offs 3.5" X 30" with one end angled off for a ramp. Several 2"X 8" by various lengths along with a assortment of blocks made from 4" X 6" barn posts. Sometimes its necessary to use a bigger block under the end of my ramp to get level.
My cedar ramps/blocks in the camper and in the trailer sheds I made in '72/'73 era. I had a neighbor who framed houses and also camped kept us supplied with job site waste.