re: Frank Lloyd Wright’s Barrel Chair

That would be one of your Masterpieces. Once you get the basic shape of the back you have to use something to shape it. A grinder with a sculpting disc?

I have a challenging project I’m starting. Maybe after that I’ll start it. 
I know the original was made from solid blocks of wood. Maybe the parts with the mortises are mortised first and then bent, or shaped from a thicker piece of wood  then the mortises are put in using a string nailed in from a certain position to create a radius.