Buy dry mortar mix that is designed for stone or masonry work.
Mix the mortar in a bucket with water. Different proportions apply to whatever mix you use, so check the directions on the package. The mortar's consistency should be comparable to brownie batter. Make it thick enough to remain on the trowel without drips. Ensure you wear goggles, gloves and a dust mask.
Trowel one layer of mortar onto the surface of where the stone will be stationed. Trowel more mortar between stones on either side.
Trowel one layer of mortar underneath the stone that you lay next. This process is called stone buttering.
Put the stone onto the mortar bed on top of the rock and push it gently into place. There should be enough mortar for it to ooze from the sides.
Remove the excess mortar from the links and smooth out the joints with the trowel.