There are undoubtedly many different ways of achieving the same goal.
I used what is euphemistically referred to in these parts as "topsoil" (that is, clayey crud that turns to cement when dry) as a base for contouring the beds and for setting the stones in place to hold them firmly. (I did consider gravel as a base but thought it would be somewhat unstable, rolling under the rocks.... ? I don't get how this would work as a base on which to set rocks, and therefore didn't use it.) The fantastic crevice garden I showed in the other post used silty subsoil as a base - in other words, material that is cohesive and somewhat coarser than clay (in other words, you can feel grains in silt, but not in clay). The construction of this garden was written up in the NARGS Rock Garden Quarterly Volume 69 #3. (N. B. These publications are available for viewing at the NARGS site, though you have to be a member to be able to see ones from the last 3 years, which includes the one I mentioned. All the older ones are available though! )
