How to build a rock retaining wall with mortar?

1. Measure the area where you plan to build the wall and mark it with a string line.
2. Dig a trench that is about 4–6 inches deep and at least 3–4 inches wider than the block.
3. Line the bottom of the trench with 1 inch of gravel.
4. Set the first row of blocks in the trench. Make sure they are level and fit snugly against each other.
5. Stabilize each course by tamping the blocks down tightly.
6. Add mortar between the blocks for stability. Once all the blocks are in place, let the mortar dry for at least 48 hours.
7. Fill the remaining space behind the wall with gravel and soil.
8. Add a layer of landscaping fabric behind the wall, then tamp it down and cover with soil.
9. Finish by adding a layer of mulch on top of the soil.