I began by building the whole chair in Rhino. By using curves, lofting, capping, dividing, and then splitting the solid to form the final chair.
I redrew the curves for the final chair since I was a bit off in the shapes of the chair as a whole and also the shape of the individual ribs. Above you can see it is rectangular from the front and top views, but I redrew it to have an egg shape, similar to the original design.
Instead of splitting the solid into the ribs. I want to influence the solid to be manipulated in grasshopper with these Design Drivers: Width of Ribs, Thickness of Ribs, Frequency of Ribs, and Direction of Ribs.
First I create the surface as a solid using my curves.
I then draw the legs in RHINO.
Then, in grasshopper I reference a curve in the middle. Apply perpendicular planes to the curve. Deconstruct it. Meanwhile, I reference the surface as a BREP. I apply the perpendicular curves in the boundaries of the BREPPED surface.
I then extend the planes, which I refer to as ribs, in the Z-axis, attaching a number slider to influence the width of the ribs. Extrude with the parameters of the BREP and then cap and voila! Baked and ready to go in Rhino world.
PDFs of the Drawings Below:
Gifs of Each Driver being influenced by Grasshopper as stated below.