[This ticket has been merged into MC-268042.]

The bug

Most of the central 8×8 region of the lectern base texture is obscured by the central post of the lectern model, and this texture is not used elsewhere. As a result, it is possible to remove this region of the texture without making the lectern look outwardly any different unless Spectator mode or other means are used to force it to be visible. Removing this region of the texture makes the "unused" region obvious.

How to fix

An easy fix - just replace the vanilla lectern base texture file with the one attached.

Further notes

With this texture change applied, it may be possible to notice very faint dark stitching around the base - this is the fault of MC-73186, which, while overdue for a fix, ultimately should not be a blocker. Fixing that issue will completely stop any of these black pixels from being visible from the outside.