I tried to do this using a ground map and the Holodeck 01 item, but, after previewing the map, I noticed that it's like some weird ground map/holodeck hybrid.
All I'm looking to do is make a full Hoodeck interior, similar to the end of that one [non-UGC] mission; those of you who have done it hopefully know which one I mean. I'm just trying to avoid spoilers for those who haven't played it yet.
There isn't really a way besides using a ground map and the holodeck detail. Just make sure the invisible walls are there to keep the player inside the holodeck detail. There is a dev made how-to video somewhere out there that showed how to use the holodeck detail, maybe that will help.
I have a tutorial on a few effects with the holodeck (see my signature).
You are limited to just that one square holodeck of a limited size to play around in though, so that may be limiting but you can hide it and reveal it at will with triggers so you can get pretty creative as long as you travel "in the program" between reveals of the holodeck itself.
I think I did something interesting with the holodeck in my mission. Keep in mind that on the shows, once the holodeck grid disappears, people can move around the arch, through the areas where the walls would be, etc. I tried to go for that.