Side vent conundrum

[Finnegan]

A while back I desnorkeled. But I had trouble getting the side grill re-installed correctly. I see the clips attached to the grill housing, and I see the slots on the perimeter of the opening, but it appears that the clips need to slide into the slots from the interior of the opening. Which seems impossible..

So now it's being held in there only by the one screw at the top of the grill.

Any advice would be much appreciated!