Step-by-step instructions on how to build low flagstone walls
1. Use a string to outline the bed’s footprint, then measure and record its dimensions, including the wall’s proposed height. Take the measurements to a flagstone supplier, who will determine how much you need.
2. Define the bed’s perimeter with powdered limestone or gypsum. Excavating or adding soil as needed, create a level foundation for the bottom layer of stones, which should be set 1 inch below ground level for stability.
3. Break oversize slabs into smaller pieces: Wearing gloves and protective goggles, use the chisel to score a line on both sides of the flagstone, then place the stone’s scoring line over the scrap wood and, using the sledge, hit the stone on the unwanted side to break it off. Set aside uniformly square and rectangular slabs for the top layer.
4. Using the largest, most irregular slabs, build the bottom layer. Place stones side by side, with straight edges facing away from the bed and jagged edges pointing in. Try to make this and every layer as level as possible; use the level to check.
5. As you stack each subsequent layer, overlap slabs to avoid vertical seams, filling in gaps with smaller pieces to make sure stones don’t wobble. For stability, angle each wall inside toward the bed 1 inch for every 1 foot of the wall’s height.
6. For the top layer, use the slabs you set aside in step 3. Backfill the walls with soil and tamp to settle it, then add plants.