Looks like veneer laminated over a form. The outer lamination looks like slices of pie. It is layed up over a male form, more layers are put on with waterproof glue then sucked down (clamped)with a vacuum bag. It's called "cold molding".
You could do it by stack laminating solid wood (then you could use the Domino for alignment)but you would need some pretty big clamps. Or find a really big tree and have at it with a chainsaw. ;D
Mike
Cool looking bikes!