KISS. You can just use a "cone of silence" spell... ... that is, take a A4/letter blank piece of paper, fold it like a cone and tape it down, then take a red l

KISS. You can just use a "cone of silence" spell... ... that is, take a A4/letter blank piece of paper, fold it like a cone and tape it down, then take a red large-tip marker and write "SILENCE!" or "BUSY" on it. You can put it upright/on-the-desk when needed, and down/in-a-drawer otherwise.