So, I had a think and came up with this. Others may already do it but I have never seen anything like it myself. ( It may be of use to others in different circumstances hence the post )



As a possible improvement I thought of making an aluminium plate with a 16mm hole to fit on the cutting surface so that it would be impossible to deform the wood with the knife. I would reduce the thickness of the block accordingly.
Well, there you have it - no measuring every case, no worries about cutting an angle and no danger of shortening your finger by rolling the case on the knife blade.