In this video you will learn how to build a retaining wall to flatten a sloped lawn. He says that if someone wants to garden but their yard is sloped and they know they can't do it, they should know that this is a lot of work. So be prepared to dedicate a lot of time and effort. You start by getting a building permit. If you're looking to build a low retaining wall you start by digging a trench a little wider then the stones and a few inches deep (the higher the wall the deeper the trench). For example if you wish to build a wall that is four feet high then you'll need to dig 2 feet deep. Make sure that you interlock all of the stones. When you've finished building the wall put some landscaping fabric behind it to keep the soil from working its way through the cracks. Then simply finish off with top soil and level everything out. Then you can enjoy your new retaining wall.