I have had mine off the ground for various reasons numerous time, including installing Correct Track & wet bolts.
Prefer to leave the trailer on the truck. Lifted with a 12 ton jack then blocked it using a very large block as a base aft of the rear wheel. Removed wheels & used bottle jack & jack stands to have precise control & support axles one side at a time. Could have lifted the whole thing, only supporting the front with the truck if I had wanted to.
Looked at the cribbing rhagfo used. Uh...no, too unstable for me. I do my refits in a boatyard so sizeable lumber is available.