I use attached, box configuration. The reason being that the unit does take some bumping when working. Are you using a regular hive body that has been modified with routed grooves? If so, then the other side of the coin is that if you don't attach, the body can then be used as regular hive body and is a more flexible piece of equipment. That does make a bit of difference when you're small scale. I just found it easier to make it a singular unit that way I know where the whole queen castle is and can just go fetch it when needed. As in most things beekeeping, personal preference and need usually drives things.