Find a parking lot that's level and see if your coach is level. If you have air bags, you might start there, get the coach level in a level parking lot..
I had a 21 ft Dolphin (the Toyhouse), I put the self sticky bubble levels on the drivers door pillar and the instrument panel where I could see them.
I could usually jockey the MH back and forth and find a position that was reasonably level without resorting to the legos.
I do the same with my 30 ft Mirada, jockey back and forth and watch the small bubble levels. If I get it withing 1/2 bubble, thats good for me (and the frig). I carry blocks of wood but have never had to use them.
2001 Coachmen Mirada (Ford F53 6.8L V10) - Toad 2001 Civic
It won't do MACH 2, but I can get a sandwich and take a pee.