I am trying to lay a flagstone patio that is roughly 15' by 35'. This patio will be right outside my back slider and there is already a 10' x 8' concrete patio there now. I do not want to remove the existing slab but like the versatility and look of a dry lay. I have heard that I can use 1/4 minus to bring the rest of the yard up to the level of the existing patio, tamp it, then lay another inch or two over the entire thing (tamped gravel and existing patio) on which to lay the flagstone. Is this an alright way to do it? My concern is settling and how difficult it is to fix if settling does take place. I am thinking of cementing in some border stone to minimize shifting. Other details that may help.. the ground is clay and very hard (I think this may limit settling), the area is very wet so I need to slope the flag I think. I have also heard of this product called Gator Dust... is that good for a dry application?

Thank you very much for taking the time to help.