I've seen it as well, but the process requires a lot of work.
You need to dig a hole in the ground, at least several feet deep, so that you can fit rocks in the bottom and allow for the whole hog to rest inside of it comfortably. Then you need to place the entire hog inside the "ditch" on top of the rocks. The problem is this: getting the coals to be on top so that it cooks from the top down so it allows for a low and slow temp. I've seen apparatuses (apparatii?) for doing this the traditional cuban way, but they do cost alot of money.
In terms of spices, cuba uses alot of sugar and spices for their pork, but I could never figure out exactly what they are.