https://www.scotusblog.com/2016/02/is-a-recess-appointment-to-the-court-an-option/
"The Constitution not only assigns to the president the task of making nominations to the Supreme Court, setting off Senate review that may or may not result in approval, but it also gives the Chief Executive the opportunity to fill a vacancy on the Court temporarily, bypassing the Senate initially, if a nominee languishes in the Senate without final action."