Covert minelaying from a merchant ship

How could a ship conduct a surprise mine attack without pretending to be a lost liner?

Use an ordinary merchant hull with a concealed bay and uncrewed underwater vehicles to place mines discreetly.

An ordinary container ship would be less conspicuous than a vessel pretending to be lost or disabled. A false bottom and moon pool could release uncrewed underwater vehicles without exposing minelaying gear. Those vehicles could position the mines, return to the ship, and let it depart normally.