I had a bag of Lynx blocks leftover from the trailer... I crushed several of them before I decided they are not structurally strong enough for our class C.
The first season, I cut a bunch of PT 2x6 into one and two foot lengths. They're heavy and take up precious storage space... they also slid frequently on slick surfaces, which was frustrating.
So next I bought a rubber stall mat at Tractor Supply - nearly indestructible - and cut it into pieces like I did the lumber. Using those under the boards completely stopped the slipping, but the storage took yet another hit.
Finally bit the $3,000 bullet last spring and had Big Foot hydraulic leveling installed. MUCH simpler... but I still occasionally take a stack of 6 one foot square stall mats for extreme off-level situations - frequent in the mountains. A couple under the lowest leveling jacks gives them a little more lift.