Levelling blocks for camper on driveway with 2 degree grade

I put one of the stackable yellow plastic blocks under each jack. It flexes a bit so the entire jack foot can be in contact with the block and the block in contact with the concrete.
A 2% grade is pretty minimal. Just use the jacks to level it or have the front a bit higher than the back.
If you're storing it for a long time, I would support the belly as well, but it's not really necessary.