Batter boards

Hope to set batter boards at my next visit. This image from shedsusa.com gives you some idea of what they look like. Batter boards are needed to square up the foundation, yielding a rectangle instead of the dreaded parallelogram. Of course, our land is not flat, and this technique will not work unless the strings are horizontal, so I got a builder's level to set string height accurately.

And (of course) we have no dirt to hold up the vertical batter boards, just rock. So, I am drilling a 4" deep hole in the bottom of the 2x4 batter boards with a 1/2" drill bit and pounding an 8" rebar into the 2x4. On site, I will drill a 5" deep hole into rock for each vertical board and drop the rebar'ed 2x4 into the hole. Nothing to it. I hope.