Spread a 2-inch to 3-inch layer of mortar onto a slab that is slightly thinner than the wood.
Lay a course of logs on top of the 2-inch layer of mortar. Press each log firmly into the mortar.
Fill the gaps between the logs with mortar.
Spread another 2 to 3 inches of mortar on top of the first log course. Press a new course of logs into the fresh layer of mortar. Repeat this process until the wall is complete.
Even out the mortar between the logs before the material dries using a mortar seam tool. Smooth out any rough spots, and scrape mortar around the logs to create an even wall.