I just printed them with the big flat areas on the bottom, no supports on the K1, so it you have some excellent bridge settings then you should be able to print without supports as well.
The plugs just press fit into the holes around the cover
I'm not actually sure how much this dampens noise because I didn't do a before and after comparison, but it looks nice.
The author remixed this model.
Simply a remodel of the other fan protector except I changed the logo to the official creality logo so it would look better with the rest of the printer.