The problem with fake stones is that their origin is very hard edged, you can't use them as masks to lower ground, unless you translate the displacement to color and then try to soften it, which is still hard.
Or you'd have to make stones a different way, by masking ground stonesized patches and raise those, add compute normal and displace sideways. Keep raising mask to sink that plane or whatever. I've been messing with that for quite some time over the years, but never found an easy solution.