Need help for building square foot garden.
I am new to square foot gardening and i wanted help on building my bed. My situation: I am trying to build a 2 by 4 bed in my back yard which is just cement. The problem that i have is that i don't know what to put as my base. I saw a video on YouTube where the person puts various pieces of wood(which are screwed to the bottom of the bed) across the bottom to keep it off the ground so it can drain. He also puts a piece of cardboard inside the bed instead of plywood to keep the Mel's Mix off the ground and then covers the inside of the bed with plastic bags. Should i follow his example or what should i do different?