How to Install Flagstone in Crushed Base Rock.
First, you will need to determine the size of your patio, by staking it out with a string line and taking into consideration the type and thickness of your stone.
Excavate the area to allow for a 3″ layer of 3⁄4 minus, a 1″–1½” layer of 1⁄4 minus and the thickness of your stone.
Lay out edging for the patio or walkway using ledge stone, plastic edging, or concrete curb.
Put a 4″ layer of 3⁄4 minus base rock. If drainage is a concern, you can use 1½ minus. Compact this base by tamping and watering or using a mechanical compactor then lay out a 1½” thickness of fine 1⁄4 minus as a bed for your stones.
If your stone is of varying thickness, add or remove the 1⁄4 minus as you go, keeping the stones level with each other and your border.
Fill the joints between the stone with 1⁄4 minus or screened decomposed granite while sweeping and watering as you go. This step will have to be repeated until you are satisfied with the finish or you can use a polymeric joint sand stabilizer.
You may also elect to fill with conditioned topsoil between the stone joints and plant a ground cover if that is the look you desire.