I have built many flagstone patios (mortared is the topic) and I have always put 4" compacted limestone gravel and 4" of concrete with rebar then the flagstone. I have read in here that some people simply put the flagstone on the compacted gravel... that seems susceptible to cracking in the near future. *and I am talking about a flat patio on already flat ground. Obviously the concrete will be 'better' but in a flat, solid soil location is the concrete just a waste of time and money? The reason I am asking this now is that I am bidding on a job where it will be impossible to get the concrete to the new patio without taking it 5g bucket by 5g bucket. (same with the stone) I appreciate the input!