There are a few threads including this one that address that. A shim is helpful if it’s equally shimmed on each side. Otherwise you have to have an eagle eye to insure the blade isn’t canted. Foam tape or chamois or some other fabric that isn’t slippery.
I have been using the double sided tape trick for the last month or so, and luckily I havent had too much of an issue with any knife being centered. THe worse one was 1 degree off on the angle cube.
