looking for a tool that adds models to a terrain based upon slope and normals

I am looking for a tool that does exact the following:
I want to align stones based upon slope and normals to form some kind of a step.
So basically, an object should point straight upwards with Z while Y aligns with the normals MINUS the Z offset.

I am aware of the procedural foliage tool and it works great but it really just places random the objects. There is no such thing as randomness :wink:

What I want is slightly different then the procedural foliage tool, because it doesn’t allow me to constrain the Z rotation. The Z rotation is always random, so I cannot at stones with an open backside to a mountain.
If that still is an option in that tool, then I don’t know how to fix it.
Looking forward for ideas, tips, suggestions.
best regards! T