It's behind/below the glovebox.

First move the passenger seat as far back as it goes.

Next, turn the small circular plastic catch on the rear of the transmission tunnel side cover so that the slot is vertical. You'll need a stubby flat-bladed screwdriver.

Slide the plastic side tunnel cover to the rear of the car and remove it. It slides out easily. Don't pry or you'll break the plastic clips.

Remove the carpeted floor cover and any rubber mats in the passenger floor. You'll need all the room possible to slide the filter element out of its box.

Remove the two Torxs-headed screws in the shroud above the passenger's feet.

Coax the shroud down on the right side near the door. It is held by just one plastic press fitting, but mine was stubborn. You want to pull it straight out. The other plastic press fitting is just to the right of the Torx screw on the left.

Remove the four small Torx-headed screws from the black plastic cover on the white filter housing. Tight clearance in the back makes a socket useful.

Remove the black cover and VOILA. Slide the filter down and out.

Install in reverse order and clean up the floorboard with a vac.

Mine was filthy after 25K miles in Alabama. I'd always thought the cabin filter replacement was just a dealer/mechanic boat payment scheme, but it looks like the filter actually does some work. We'll see if if makes any difference in the AC.