For awhile I had to piles of dirt that I drove up on with enough room between the piles to squeeze myself into. That worked great for years, but then I cleaned up the place and it's all lawn now.
I built ramps out of 2x6s. Bottom piece is about 2.5ft long. The next piece is 2 ft long, etc etc. In total about 5 pieces that get the mower (or car) about 7.5 to 8 inches off the ground.