First thing to do is to loosen the rubber gasket which protects the Punk from Dust and moisture (to a certain degree). Use a spudger or similar tool for that

and move it all the way along between the Punk housing and the gasket

Once the gasket is loose and there is no adhesive holding it to the Punk housing, simply start pulling it over on the Punk housing.

The gasket will not yet come off. It is still attached to the Punk housing by the front grill.