Had Bigfoot automatic leveler on our fifth, manual leveling on our TT (sigh). Read a blog post written by a guy that has been RV'ing over 40 years that suggested a fairly easy method to level with 2"x8" planks.
1. Measure hub hub to hub distance of the axles. Add 18".
2. Cut first plank to the measurement obtained in #1.
3. Add 5" to measurement #1, cut second plank.
4. Add 5" to measurement of second plank, cut third plank. In his experience the writer stated he has never needed more than three planks.
I followed his idea and to date has worked great, and I've never needed more than one plank. They are not heavy and the tires of both axles on the low side are fully supported. Carry them in the truck bed. Works great on soft ground or hard surface; didn't even need to angle cut the ends, the trailer rolls right up on them, I tried it with 3 planks stacked. The trailer rolled right up on them and the planks didn't move.