Interspersing pavers with grass, you'll want to bury the pavers to the same depth as the soil line so that you can mow right over them. For greatest stability, it's best to excavate deeper than the depth of the paver itself, and put down sand as a setting base for the paver. If you place the paver directly on the soil, it is more likely to shift and heave. However, resetting the shifted pavers may be less work than deep excavation in this case.