Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

Attach fragmented phrases or turn them into sentences
Repair sentence fragments
Grammar

Like subordinate clauses, phrases function within sentences as adjectives, as adverbs, or as nouns. They cannot stand alone. Fragmented phrases are often prepositional or verbal phrases; sometimes they are appositives, words or word groups that rename nouns or pronouns. (See 49a, 49b, and 49c.)

Often a fragmented phrase may simply be pulled into a nearby sentence.

If a fragmented phrase cannot be pulled into a nearby sentence effectively, turn the phrase into a sentence. You may need to add a subject, a verb, or both.