Slide both front seats forward. Stand in car on rear floor facing forward. Grab lower edge of rear cushion and pull up as you kick lower edge of cushion with your heal rearward.

I have tried that but I will give it another go.

If the last suggestion doesn't work, with the front seats out of the car, sit on the floor, facing the rear seat push with both feet at the same time, do one side at a time, it may help if someone else pulls up.

Well, I may need to see a chiropractor but I did get the seat out. It was worse than wrestling a bearcat.