Yep. You bury it, add some enzymes, toss in poo and let nature take its course. I'm not sure this is what you have, but the dimensions sound correct for an old one.
You can find the more recent incarnation here:
http://www.doggiedooley.com/
I'm not recommending them. I considered getting one because it sounded easier, but I heard from a couple of people that they stink.