Adjust the miter saw to cut a 60-degree angle by sliding the table and tightening the handle once it is at the 60-degree mark.
Lay the cedar boards flat on the miter saw one at a time and cut each end at a 60-degree angle. Cut the angles on the same side, so that one side of the board has long points. The boards will fit together at the cut edges to form an equilateral triangle.
Place the boards together forming an equilateral triangular assembly. Drive three evenly spaced stainless steel wood screws through each corner joint fastening the assembly together using a screw gun.
Center the landscape fabric over the triangular assembly. Trim the fabric with a utility knife so that it fits the assembly. Staple the fabric to the edges of the assembly using a staple gun that is equipped with 1/2-inch staples. Space the staples every 2 inches along around the entire assembly.
Lay the hardware mesh panel over the landscape fabric. Cut the hardware mesh to fit the assembly with metal snips. Screw the mesh to the assembly with a screw gun using washer-head screws. Space the screws every 2 inches around the entire assembly. This is the assembly’s bottom.
Turn the assembly upright. Fill the first 2 inches of the bottom with gravel. Fill the remaining depth of the planter box with potting soil.