If you start with a small colony, you can place it against one of the side walls. A follower board can be placed at the edge of the colony. This means that the bees have a smaller space to heat and raise the brood. As the colony builds up the board is moved along and new frames are added to the colony. If you are feeding the bees then you may need to cut a new hole in the inner cover above the bees. Reducing the entrance to a small one near the bees would help.