Well, I tried your practice idea, and I created a plane, made sure to press 3, then I and enter, then I again and enter, then G and Z, and then E to extrude, then I toggled object mode, and it worked there was a cut between the inner extruded part and the rest of the plane just like the speaker but again when I tried it on my console in object mode and x-ray off it only shows a solid plane?
Also, I did the Blender 4.5 basic course, then suggested at the end to do this Press Start after my plan was first to do the Core Modeling course, and choose my own project that is not part of the courses to test what I learned, then after the next Core course etc.
