Level the ground where you want to build your retaining wall with your shovel. If you are leveling a very large area or an extremely uneven surface, you may need to use a tractor.
Lay the first level of concrete bags out where the wall will be built up.
Stack the second level of concrete bags on the first level. Stagger the second-level bags over the bags on the first level. Do this by placing the center of the second-level bag over the divide between two bags below it on the first level. Shift the bags back about 1/2 to 1 inch towards the hill that you are building the wall around to give the wall extra strength.
Repeat the stacking process described in Step 2 until you have stacked five levels of concrete bags.
Spray the concrete bags with water until they are completely wet.
Let the bags dry for 24 to 48 hours.