Now for some fiddling and prying: The internals can be moved away from the front. If you are still holding the structure upside down, with the dot facing towards you, you should be able to move the black parts away from the aluminum, pushing forward. I recommend prying something in between the two layers and carefully opening it up.

Keep in mind that there are two rails running on the inside (you can see them if you peer inside the cage). You will have to follow the same direction.

After a while, you should be able to slide it open.