How to Mortar Set a Pathway or Patio with Flagstone.
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 a depth of 6″–7″.
Lay a 2″ base of 3⁄4 or 1½ minus base rock and compact it thoroughly.
Form, pour and screed a 3″ pad of concrete.
When the cement is beginning to set, take a coarse broom or steel rake
and roughen the surface to aid in the adhesion of the mortar bed and stone.
Lay a 1″ mortar* bed, screed level. Screed only as much mortar as you can lay stone on before the mortar begins to set. Stones should be free of any dirt or debris.
Apply a neet cement** to the back of each stone just before laying.
Set your stone, leveling as you go. Tap stones with a rubber mallet to level and provide consistent contact with the mortar bed. Compensate for the variations in the thickness
by adding or removing mortar as you go. Try to keep your joint spaces about 3⁄4″ or so and avoid long, continuous joint lines.
Grout*** joints with a float. Clean excess grout from stone with a damp sponge before grout sets.