Article II, Sect 2 – President can make recess appointments, but they have to be confirmed by the Senate. If not confirmed, they expire.
NOTE: Another reason why holding the Senate was KEY.
https://constitutioncenter.org/interactive-constitution/articles/article-ii
The President shall have Power to fill up all Vacancies that may happen during the Recess of the Senate, by granting Commissions which shall expire at the End of their next Session.