How thick should my concrete base be for my flagstone patio?

by Shawn
(Queen Creek, AZ)

We're going to be laying a flagstone patio area in our backyard. I feel confident in all aspects except one, our concrete base. I have read online that the base should be anywhere from 1" to 6" thick. We are trying to stick to a tight budget, but don't want to do it "cheap". If 2" is sufficient but we use a base that is 4" thick, that will obviously double the cost for that part of the project. We are curious as to how thick our base foundation should be for our patio. Any advise would be greatly appreciated! Thanks!