Building A Stone Retaining Wall Without Mortar!

Step #3: Backfill with rocks:

Once the base stones have been set, use smaller rocks to fill the gap between the base stones and the hill.
Use “bad” rocks for the backfill. Save “good” rocks for using on the front face of the wall. (good rocks are typically rectangular, with flat faces which make them stack easier).

Step #4: Pack with gravel and soil:

Backfilling with rocks will fill the majority of the space, but there will still be small gaps in between the rocks.
To fill these gaps, pour gravel over the backfill rocks and massage them into the cracks and gaps.
The final step is to add a thin layer of soil or dirt over the gravel. Tamp this down. Now you have a nice flat surface to start the second layer of stones.