there are definitely stds for this, and some may include both rock and
screeding materials, if not more than 2 layers, possibly of diff thickness'
and grid mesh sizes. Depends where it is, and what its doing. The only
thing I have heard sand for is in the days after the stones are laid, when
you tamp the stones if necc and for brooming in between the cracks, even
annually. Limestone screeding is the fine stuff that packs and when wetted,
becomes hard, but won't completely fill between the gaps. It takes time but
sand will make a grout -like bridge between all stones. Possibly sand and
definitely dirt will allow grass, moss, weeds to grow through over time. If
it was a driveway, and more Z-brick stone-sized brick, and I think if you
used sand, you would see tire track grooves over time. Pathways can slant.
Done right it would be a permanent feature of your landscaping, and can be a
totally flat platform, if poss.