I built these sort of wedge/chock thingies by layering up pieces of pressure-treated 2X and screwing them together:
https://www.skoolie.net/forums/f11/r...tml#post407876. I back up past where I'm going to park, maneuver these beasts into place (destroying my back) and then drive up them. The biggest one is about a foot up and I would not want to go up any further than that with this kind of thing. My biggest fear is forgetting I'm up on them and driving off the front instead of backing up, which nearly happened once - I had it in D before I remembered.
I have to say, you are really really going to want your bus level. I usually drive my bus to my house where it's perfectly level and work on it there. When I have to work on it up on the chocks (which don't have the bus quite level) it's annoying and tiring to have to walk slightly uphill to the back every time; when it's just on the ground at my lot it is so much worse.
One good thing is that the slope will really expose leaking windows. The way the windows are designed, the outer sill will pool water on one side if the bus is angled, and pooled water will find its way through openings.