I haven't seen their page, but I've seen this kind of thing before. After lining up approximately where things should fit, one piece is cut in a smooth curve ju

I haven't seen their page, but I've seen this kind of thing before. After lining up approximately where things should fit, one piece is cut in a smooth curve just back far enough to remove the live edge. The other piece is cut to match that. This can be done using router templates. IIRC there's some trickiness with the size of the router bearings / guides to account for cutting on one side vs. the other. For the scale they are doing, they might be able to set up a more customized solution. For example, a router attached to some guide tracks like a https://en.wikipedia.org/wiki/Pantograph https://en.wikipedia.org/wiki/Pantograph