I live in Southeastern Oklahoma where the ground cracks from the heat every summer. I am going to build a flagstone patio around our inground pool, but I need to know whether it is better to build the patio on sand and crushed rock, or a concrete bed. Or if it’s better just to use sand and dirt beneath (for the old-world style, moss between the flagstones look – which would be nice)? However I build this, it needs to have excellent drainage and be an even surface for patio furniture. Also, once the flagstone is set, is it better to mortar between the stone? I don’t want everyone getting sand or crushed rock in the pool.