You probably want the AL housing plated with something....like copper/nickel, maybe with a gold or solder flash on top.
Then you can either epoxy the board in (ablebstick makes a sheet of silver conductive epoxy that you can cut to the dimension of your inside housing), or solder it down.
You could just glue it down to the AL bare surface, but it will not be a good DC electrical connection if you are using active devices. For that matter...even grounding via holes need a good electrical contact to work. MOST conductive epoxies will NOT adhere properly to a raw aluminum surface.