Remove back seat
To remove bottom part of the back seat, simply pull it up around the marked area.
Bottom part removed. It was held in place with these metal catches.
To remove back cushion, first unscrew two screws (torx size 50) located at the centre of the cushion.
Then, to release the upper part of the rear cushion, unclip two metal hooks accessible from inside of the boot.
Just push it to the side with a flat screwdriver until you hear a release sound.
Repeat the same on the other side.
After this, simply maneuver the cushion out of the car. A help of another person helps, but is not necessary.