ive been reading different ways to install flagstone patios, the company that i work for uses Oak select flagstone and lays it in a 3-4" mortar base over and 8" sub base, ive been reading that your supose to use a concrete sub base and was wondering which way was correct, also im wanting to install one for my girl friends parents and they want to pay me but im not sure how to charge, ive installed tons of them but never bothered to find out how much they cost