I would use these steps for something like this.

1. Start by roughing out the shape using a box with fairly low detail.
2. use extrude edge on all the exterior edges and cut around the corners and use backspace to remove the edges forming triagles at the corners. (see my image)
3. use extrude edge again on the bends in the seat.
4. add turbosmooth and maybe experiment with a relax modifier aswell.
5. then manually add detail to the bends and move points around to give it the natural folding look.

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