It's just right behind the steering wheel or on the left of the park button,looks like a vent of some sort or may be it has to do with the remote.
My guess would be slots to accommodate a glass breakage sensor microphone (dealer accessory) installed behind that panel.
The microphone is high up, in the headliner somewhere, around where the map lighting is. This, in my opinion, is too low to be a microphone. See my previous post as to what it is.