We use two different approaches one for tire side to side leveling and the other for rear stabilizer jack blocking.
For the tires I purchased 2 8' 1x10 Azek boards from Lowe's. I then halved them on a 45° to bevel them. I created a pocket in the bottom board and set a wide load binding strap (found on the Dalton Hwy) in the pocket. I then screwed them together to form a pair of 1½" planks. The straps are long enough that the farthest wheel anchors it prior to the closest wheel climbing onto the boards. (They do not scoot even on wet grass.) I attached the leftover cutoffs double thick to the landing pads.
For the leveling blocks I use metal guardrail, wood standoff blocks. They can be duplicated by cutting up broken posts for the same guardrail.