Dig a trench a little wider than the retaining wall you are using 3 – 6 inches, fill with slag sand and tamp with hand or power tamper.
Start with the first layer of retaining wall making sure to use a level as you go. Depending on your design you might need to make some cuts. Proceed until you have a finished product.
For more than one layer, or when you are using a cap, it’s recommended to use a retaining all adhesive. Proceed until you have a finished product.