Formal:
* Deliberate: This emphasizes a slow, careful, and thoughtful way of speaking.
* Measured: This implies a slow, steady pace with a controlled rhythm.
* Unhurried: This emphasizes a lack of haste and a relaxed manner.
Informal:
* Drawl: This refers to a slow, lazy way of speaking, often with a specific regional accent.
* Drag out: This implies speaking slowly and with exaggerated emphasis.
* Mumble: This refers to speaking softly and indistinctly, often slowly.
* Slur: This implies speaking slowly and unclearly, possibly due to intoxication.
* Tarry: This implies speaking slowly and lingering on words.
The best word depends on the context and the specific effect you want to create.