srjohnt:

I'd check into this:

Here is a link that might be useful: Ditra drain

One of my projects was taking kitchen counter-top scrap and placing it on a concrete slab. This solved a problem for the cost factor that the buyer wanted. He wanted a flagstone patterned, flattened, non skid surface that he could drive on with his vehicles and had natural stone. Doing this is labor and cost prohibitive using traditional 2-3in flagstones laid in sand bed with cement grout mortar as they are too unstable for vehicles to maintain integrity. Instead we did a cement pad to support the vehicles and laid a veneer over the top with the 1 inch scrap sedimentary types of stone. Then the polish was sand blasted which was messy but allowed use of larger pieces without slippage on the surface. The workers appreciated the less weight and inc safety of using the scrap as the same surface size could be manipulated by one person instead of 2-3 with traditional flag stone. Here is a picture of the finished site, not exciting but very utilitarian.

LOL...he could probably get the same effect with stamped/stained concrete, but he wanted that natural stone...Very happy with the product

Well, Thanks to everyone who replied. I didn't get any specifics on "how to do it", so here's what we did, and so far, so good.

I figured this was somewhat like a tile job, but with heavy tiles (3" thick) and mortar instead of thinset. I couldn't find a trowel with notches larger than 1/2" so I modified one of those with a grinder to 3/4. Mixed a rich mortar mix with bonding admixture, then troweled the mortar with the notched trowel, and laid the stones with a 78 inch level. It came out really well. Perimeter stones are laid, and field stones dry laid for size, We'll finish up tomorrow.