Based on the thought, I found something interesting in resin: resin is usually liquid, so, it is able to control the thickness. When the cured resin is thick, it is more rigid and stiff; when the cured resin is thin, it is more soft and flexible. Also, the material property could be gradually changed by giving a slope in the mold.

In that case, I want to make a ellipsoid which has 1 inch thickness at the bottom and gradually changes to 1 quarter at the top. According to the assumption I made, the ellipsoid should be rigid and structurally supported at the bottom, and should be soft and flexible at the top which allows people to seat on, theoretically.