Here are a couple of hanging planters I made using two redwood boards. My local lumberyard sells six foot “fence boards” in a couple different widths. I used one 8 inch wide board for each of these planters. The great thing about those boards is that they are pretty cheap. Each one cost a little over $6.00.
I can tell you this, it was a lot of repetitive cutting! I guess the key is just to work out some sort of assembly line and keep organized.