The back seats split in two. There are two bolts at the corners of the seat. Undo those bolts. Now go to the opposite corner of each seat (should be middle of your car) you will see the hinge part. that is Like a locking mechanism. Lift it up to the bigger hole. Go back to the end you unbolted and pull away from the center of the car you might need to give it a good tug but they will come out.
Unless you have checked already. I think the back seat area is smaller then the trunk opening.