If I remember correctly, it worked in the opposite manner from Quake... You started with a large block. Then you carved out the sections you wanted for a level, like a giant cave. Supposedly it made VIS leaks near impossible. I didn't like it much.

Yep, that is exactly the way it works. It does take some getting used to since it is the exact opposite from every other 3D editor (game or not).

If anyone wants to work with the editor enough to see how hard it is to make a level, Unrealty has a demo of their editor available for download. This is almost identical to the UnrealED in the way it works, so tutorials and such should be able to be followed in it.

My last huge attempt to make a map was back with the BUILD engine in Duke3D. Now that was an odd method of making maps...

Edit: I just talked to the person who made Unrealty, and he said making maps for Quake 1 will probably be easier. For your purpose it is probably what you will want to go with.