We camp in a lot of spots that may require digging one side down if allowable and block up the other. Its not just simply add a certain board thickness. Ramps have to be made from different size boards to get level and pull or back the rigs tires on. Then I drop the front landing gear and rear stabilizers.
I have taken the wheels off the door side to get level on a two week stay. I'm equipped to do that and that trip was fantastic/no crowds or barking dogs. A dream trip.
If we can't dig one side down that means blocking up one side even higher. Yeah I carry lots of lumber. My favorite is a pair of 4" thick x 10" wide cedar block around 30" long I chainsawed a drive on slope on one end so the tire rolls easily up on it. It also can be turned over for a tall ramp.
Now if your staying in RV parks or newer campgrounds with leveled/flat parking sites then the process is much simplified as others have pointed out.