I've got an observation hive that has maintained a very small population level. When I first created this hive by taking some frames from an existing hive, I think I lost the bulk of the bees to "drift"--- meaning, they left the observation hive and went back to their previous home.
So, with such a low population this hive leads a hand-to-mouth existence, and I decided to treat them to a full frame of capped honey from one of the hives I got out of the almond orchards. I like doing it this way, as opposed to feeding them sugar water.
This observation hive has a wooden "tunnel" that leads from a bottom entrance (a hole in the upper circular swivel baseboard) through a wood panelling of the wall's interior, and the stucco of the wall's exterior. That's how the bees get in and out without entering the room.