This is what’s in my den. Recently widened to make room for another row of brushes.
The slot for my glass shelf can accommodate the piece of 26 gauge galvanized duct metal.
I put “returns” on the three sides not slotting into the bracket. That takes care of the sharp edges. And gives the piece sufficient rigidity for when you remove the brushes. For it not to flex.
My other brushes I’ve just used magnets from the Depot. That come with 3M adhesive fasteners so they can hang like my more modern handles.

