I would probably build a open baffle speaker with a full ranger with an integrated h-frame or dipole sub. I have been wanting to try something called a slot load as well:
The guy in the video runs this outfit https://www.lathamtimber.co.uk/products , and sells a whole lot of interesting decorative products including Valchromat. Different thicknesses and panel sizes.
Wonder what the acoustic properties are like? How dead etc.
Just seen this on his site "Please note: due to the nature of our business and our delivery vehicles, we are unable to supply to the general public."