We did test fits. I designed a cut file that was kerf adjusted to be 4.3” square with 1/16” radius corners to match his CNC bit.
He took those test engraves and worked out pockets that fit them pretty exactly.
Even with that he did some fine fitting with a hand plane, shaving off just enough from the album covers to get the fit the way he wanted it.
The trickiest part was using solid maple for the albums, it was prone to warping and humidity changes. If we did it again we’d likely use maple plywood.