I stopped by designKLYK’s booth at ICFF and got a demonstration of their Jacob Chair, which is more of a lounge. A polyurethane foam cushion covers a plywood base, but the cushion is constructed as a Jacob’s Ladder, so that it is double-hinged and one cushion can fit perfectly into the chair’s specially-designed notch. Designed by Kanjiro Yamakawa.
Here is a video of the cushion: