Looking for advice/ideas on the best way to lay 2 1/2 inch thick concrete pavers over concrete slab. Pavers are the interlocking type w/ a 'preachers hat' pattern. I was planning on laying pavers with thin set mortar mix, but a friend said they hired a landscape co. to cover a cement patio w/ pavers and they used sand between the pad and the pavers. Any advice would be appreciated. Thanks for the help.