Not getting much back there, believe me, I'll try, but I just have my doubts.
I could cut it flat at the base, then fill it back in as I work my way out, but not sure about that either.
Size of rock sounds good, I'm just thinking that with the fabric the rock would just about roll right down the slope. Obviously, start at the bottom. Guess it might be ok, just haven't had to work with that kind of slope in such a tight space before.