I made a box for my new fruit trees from a pallette that was being thrown in a skip, and found it was really easy. The pallette came apart and I could reuse many of the nails. The thicker supports come from the base of the pallette and it needs two pallettes to get enough wood for the box. After this I lined it inside with food grade pvc and drilled an outlet hole incase it gets water logged but you don't need to do all that if you didn't want to, however the box lasts longer and I'm hoping the tree will need less water. I also sealed the wood with wood oil which made it darker in finish.