Mix the mortar with water according to the manufacturer's directions. When properly mixed the mortar should be the consistency of cake icing. When placed on an upside-down trowel, the mortar should not fall off.
Smooth out a ½-inch-thick layer of mortar onto the surface where the stone will be installed. If the stone is going to be installed on a wall, tightly wrap the wall with wire mesh first.
Run a notched trowel through the wet mortar to create a groove for the mortar on the stone to bond with.
Butter the first stone to be placed by layering mortar on the bottom of it approximately ½ inch thick.
Press the stone into the mortar and wiggle it back and forth to settle the two layers of mortar into each other. Mortar should ooze out from under the stone. Wipe the excess away using the trowel.
Layer the top and sides of the first stone with mortar.
Repeat steps 4 to 6 until all stones have been placed. Place the next row of stone, centered over a joint between two stones in the row below.
Allow the mortar to dry for 30 minutes. It should not be completely dry. When touching the mortar after 30 minutes it should leave a fingerprint.
Brush the mortar between the joints smooth.