I purchased the set of 3 "Hockey puck" under cabinet counter lights. The instructions do not say how the lamp housing is removed from the Surface Can so that the Surface Can can be mounted under the cabinet. The lamp housing tabs seem to be restrained plastic walls and cannot be rotated to the slots.

They are slot locked. Hold the bottom and twist the top to the leat. They should separate. You should see 3 screw holes for mounting the base to the cabinet. After installing the base, put the top on and screw to the right. Connect the wire looms together and the main lead to the transformer.