Oral posture refers to a dialect or accent's "home base" in terms of articulatory settings - specifically the jaw, the lips, the tongue, the cheeks, and the velum (soft palate).
JAW: Raised but mobile
LIPS: slightly pinned at the corners, but are free to retract and trumpet for certain vowel sounds
TONGUE: Active back body of the tongue that retracts often to achieve the rhoticity in this accent
Oral Posture Quick Tip! The Hesitation Sound
A clue to a speaker's oral posture can be their thinking or hesitation sounds, something every speaker has.