After designing this same basic planter a few times, first by hand, then with openSCAD, I made a web app that lets you input the parameters for making your own. It exports SVG files which can be cut with a laser cutter or, in my case, with a shapeoko CNC milling machine. Try it out here
If you are using a Shapeoko and have access to Easel, you can import the SVG from the above step and simply select all paths and mark them as “Outside”.
Make sure to set the material height to the exact height of the material you are using.
Simply press “Start Cutting” if you are using Easel.
If you are using MakerCAM or other to generate paths, download the gcode and import it into a gcode sender program like Universal Gcode Sender. Then send it to your machine.
Just put the three sides together first, then plug them all into the base. Then just fill it with soil and plant!