The fridge needs to be 3* side to side and 6* from front to back, both as standing looking at the door of the fridge. In most units, this means the side to side is front to back of vehicle. If you do the calcs, basically this means the front tires must be within 8" of the rear tires and the left tires needs to be within 8" of the right tires. Generally, if you think the camper is level enough for you, it's level enough for the fridge.
Depending on how much I'm out of level, I will use blocks on 1 - 3 wheels, but usually on 2 wheels. When using blocks under just 2 wheels, it is common to put an extra block or two under one of the wheels. This means I get say front lift with a bit of side tilt too. Some will argue this puts a strain on the frame, but if you are only doing this by a 3" or less, there is very little strain as the suspension takes up most of the difference.
I have a SRW which makes things a little easier, but I would do the same if I had a drw, would just need an extra set of boards for the extra rear wheel. I also carry more than most need because I sometimes take a bad site for the view. I carry two 4x4x12, two 6x8x10, four 2x6x15, and a set of 8 lego blocks. The 2x6 work as boards or ramps up to the 4x4 or the larger block. The larger block can be put on any of the three sides for a variation in height. I can also use the lego blocks with or without the other blocks for additional height variation.
Worst case is I've had the front wheels 16" off the ground. Just one of the reasons I have a 4wd is so I can put it in low range to help crawl up on the boards. Keeps from kicking the front blocks out from under the wheels.
But generally, I find most parking lots are level enough at some place not to require blocks. I also try not to put it up on blocks in parking lots because it draws attention that I'm not just there for a short while.
Nice thing about wooden blocks and boards, they are very cheap so no big deal if you leave them behind, just an inconvenience.