David Ross wrote:

.... If you live in an area where freezing is a problem, you
will need at least a gravel foundation under the DG. Then you will
need extra DG because it will work down into the gravel...


You could install landscape fabric between the gravel and the stone
dust. This will allow the gravel to provide drainage (so the freezing
doesn't heave the subsoil) and prevent the stone dust from making the
gravel impermeable.