Level on sloped campsites. How? Unique to 5er's

Dutch you need a set of these
Harbor freight 12 ton jacks




These will support the weight of the trailer while you place your blocking and extend the legs.
I used these jack to support my trailer when one of mt jack legs failed. They are very stable.
If you are running into this issue frequently, they are a good tool to have in your arsenal. They will be more stable and more convenient vs. carrying a lumber yard of blocks.