Use Bluestone driveway gravel about 3" deep. Bluestone is a universal drive stone used everywhere. It comes in different sizes but I'm not sure what they are. You really should use a base to keep the stone from sinking into the ground. Crush & run or stone dust tamped down very well. For the border, I'd use the plastic garden edge you can buy from the big name home improvement stores. Lanscape timbers attract insects (ants escpecially). I replaced all the landscape timbers around my gardens when I bought my current home and there were millions of ants colonized in them and nobody wants these pests in their RV. Also consider drainage and runoff. If needed, you can use a French drain. 6" perforated drain tile will work. These heavy beasts need support when parking them on earth. Even with 3 inches of stone, they'll continue to sink unless supported with a base. JM2C.
2013 Jayco Eagle 328 RLTS
2012 Ford F250 6.2L 4x4 CCSB W/Air Lift air bags
2002 Coleman Bayside Elite (traded)
Me, Momma and Charles (RIP buddy)
And introducing Sofie!! ;)