Success!

Inside those two large holes behind the two bolts are two plastic screws. You turn them 90 degrees, and that whole black part there snaps out. It was a bit tough getting it all back in, required a bit of force.

I think the screws were replaced by latches at some point.

The original filter in the car was about 3 times as thick as my new one? *shrug* Also doesn't look like it's been changed since.. ever!