It's like one of those chinese puzzles - no force or bending is needed, but the first couple times expletives can't be helped.
Seems every time I do it, I have to learn it all over again. First slide the seat back off the pins. The part I can never remember is whether the front or the rear has to come off first. It takes wiggling the seat around a bit to get just the right angle, and you'll then be able to slide a hinge past the frame. Then get the other one.
They won't both come free at the same time. I seem to recall the front coming off first, but don't count on that.
Some had clips on the pivots to prevent the hinges falling off, so make sure to remove them. They're not really needed, though if you're not careful when opening the seat, that can happen.