Any patio requires a certain degree of excavation to ensure there is a proper base beneath it. It all depends each specific situation but it usually entails 12" of excavation, compacting existing soil, rolling out a fabric underlayment to ensure stability and the that area is filled with class 2 or 5 gravel, crushed concrete or rock and compacted thoroughly with a jumping jack. It is during this process we can also install any required drainage pipes or conduits be it for gas, electric or just for future add-ons. We then fine tune screed that base material , go over it with a plate compactor and then screed out 3/4"-1" of fine bedding material usually fine granite sand. It is only then we are ready to lay any paver/stone material on that pad. After the patio material is on the ground and any cutting is completed we install edging along the patio to keep it locked in, sweep sand in between any joints, on paver patios lightly vibrate the sand into those joints, and then finish any necessary dirt work along the patio.