Yeah actually that's not quite right. Planter boxes are one of those things where people think you just nail four boards together and call it a day. But if you don't cut the corners at a 45 degree angle the water pools up and rots the wood in like six months. Also you gotta drill drainage holes in the bottom or your herbs will drown. I learned that the hard way when my basil turned yellow and died within two weeks. So really what you probably did wrong wasn't about skill it was about skipping the little details that make it actually work. If you ever try again just remember that the joints matter more than how straight the sides are.