A number of controllers, such as some models by Blue Sky, require they be fit into a panel or mounted into a box. They are fairly large and many boats simply don't have enough room near the panel to mount them.
In a situation like this an inexpensive weather resistant electrical box, about $10.00, can work well. I simply use a multi-tool, Fein, Milwaukee, Dremel etc. to cut the face to fit the controller.
When the banks are full these Blue Sky controllers can give off some serious heat. Be sure to mount them so they can dissipate it well. The aluminum front panel on this controller is the heat sink.