https://www.heritage.org/political-process/commentary/can-the-president-adjourn-congress-and-make-appointments-without

>In 2014, the Supreme Court said in NLRB v. Noel Canning that three days is not long enough to allow the president to make recess appointments. The high court held that a Senate recess or adjournment has to be at least 10 days before the president may do so.

>For the president to use the Adjournment Clause to adjourn Congress for the 10 days needed to make recess appointments, there needs to be a formal disagreement between the Senate and the House. The Senate could pass a motion of adjournment for at least 10 days. Under Senate Rule 22, such a motion isn’t debatable, so it requires only a simple majority vote.