Museum bench designed by Michael Hurwitz, how did he do it??

In February 2017 of Fine Woodworking magazine there is an article about the subjects museum bench. The article states that he did a mock up in poplar using 2X stock. To me, it looks like the angle on the underside of the seat is about a 9 degree slope from the center to the edge, with the one end at 1 1/2 ” and the other at 5/8 or 3/4. How is this done? I’d like to try and make it. I am thinking he used a bandsaw, but I really don’t know and i don’t have one. In the article he says the curves at the edges are a combination of coping cuts and some chamfer cuts on the table saw, I get that.
Your help is appreciated. Thank you

Steve in AZ

-- Steve in AZ