The one sentence that forces deck clarity is this: "This presentation exists to get [specific audience] to [specific decision or action]." If you cannot finish that sentence cleanly, the deck is not ready, and no amount of formatting will fix it, because the problem is that you have not yet decided what the deck is for.

The sentence works because it exposes the two things muddy decks always skip. First, it names the audience, which forces you to build for the actual people in the room rather than for a generic everyone. Second, it names the decision, which forces the deck to have a destination. A deck that only informs has no destination, so it wanders, and the room feels the wandering even if they cannot name it.

Once the sentence is locked, it becomes the test for every slide. If a slide does not move the named audience closer to the named decision, it is not earning its place, and it should be cut or moved to the appendix. That is how the sentence turns clarity from a vague aspiration into an editing rule you can actually apply.