Thanks to all who replied to my previous question. Clearly, I've got some work to do. :)
I've settled on a pair of 2ftx8ftx2ft high boxes to start the spring. As for the wood, I'm considering PT for the rot resistance but something nagging in the back of my mind remembers outgassing of formaldehyde from PT?
Also, the question of what they get filled with is kind of important and I've been unable to find anything resembling a consensus. My current thought is 1/2 topsoil and 1/2 aged horse manure as a start.
What else should I be looking at?