OFF TRUCK FLOOR SUPPORT?

Storing at home, I use concrete house blocks, 2x high, with 4x4 pine on top. One set at the back, one at the skirt transition, another at the front.
Bigfoot has a sketch in their owners manual.
I couldn't trust sawhorses.

There is huge difference how to handle less than 1000 lb camper and how to handle >6000lb camper.
Big camper usually have very strong rear bumper, who work well in supporting the floor, while on front -fresh water tank is pulling the floor down when on jacks.
I used to have 4x6, that I lately replaced with aluminium beam that I put under front wall of the camper. Easy to carry and adds a lot to stabilization.
I adjust the jack to spread the weight between them and additional support.
This way the camper sides keep the horizontal level without sagging this way, or the other.

Depends on the camper.

You can sometimes get an idea of what's necessary by looking at the floor structure of your camper. On mine, the floor is a single layer of OSB/chipboard, with what look like metal fence posts running width-wise about every 12".

In my case, I'd be a little leary of walking on that floor unsupported. Two sawhorses would not work, as arranged width-wise, they would just punch up through the OSB or only support one cross member each depending on where you put them. Arranged length-wise, they would only support about 1/3 of the cross members.

In my case I use two 8' 4x4 timbers laid across the sawhorses to support the floor when I'm storing the camper. This has the added benefit of being a backup to the jacks in case one fails.

A couple of strong saw horses with a sheet of 3/4" plywood.
Two stacks of pallets.
Four 55-gallon drums with a sheet of plywood.

Bill

Some campers, Lance comes to mind that are self supporting (strong floor construction) and can be used off truck. Others aren't.

I store mine in the off season in the barn on the jacks with no issue and nothing underneath the floor.

I use 2 saw horses and the four jacks that are on the camper. I also screwed down two 4ft 2x6's across the tops of the saw horses.
I try and drop the camper onto the saw horses and jacks evenly, not sure how good my eyes are at doing that but a try.
Half the time the camper is just sitting on the camper jackets and that's it,
Soup.