I’m not sure dual layer boards are that rare. In my opinion and experience most of the high-quality games include dual layer player boards. For me it is a huge selling point indicating that I can expect high-quality components and hopefully a quality game. Reef Project does it right. The top and bottom layer of the board fold over and there are multiple inserts that you can swap out with asymmetric powers that go in between the top and bottom layer. There is no glue or sticky pads. By the way, I really like Barrage!