The work from artrager is indeed great. I suspect that he did the stones and grass in 3ds Max.
You could PM him, perhaps.

Regarding alternative 2, I think you did some unnecessarily complex procedures. You don't need to swap the negative cubes. I would suggest these steps, I think these are the easiest and safest:

1. duplicate your cube-stones so that the copies are in the exact same place as the original ones
2. boolean subtract the copies from the ground
3. bake the result (to eliminate some stray pieces that sometimes remain)

The original stones are never touched.

Regarding alternative 1, what was the result?