How does one pronounce the intention for fasting a makeup day?

The intention resides in the heart, not the tongue. Uttering it is not prescribed; rather, it is considered an innovation by many scholars. It does not require verbal articulation, by agreement of the Imams of Islam. So, whoever intends to fast tomorrow, at any point during the night, has made the intention. The intention must be specified for every obligatory fast, such as a make-up fast, expiation, or a vowed fast, by believing that one is fasting tomorrow of a specific type.