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: limited range of motion and fairly raised
TONGUE: The back body of the tongue often retracts
CHEEKS: There is little buccinator engagement, meaning the cheeks tend to be relaxed.
LIPS: Slight lip corner tension with a tendency to slightly protrude the lips.
This clip provides a great demonstration of the relaxed cheeks and lip protrusion in this accent.
Oral posture in action in both Russian and English.
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.
[ a̠ ]
The audio and video clips demonstrate a hesitation sound from a couple of different Russian speakers, which can be described as a retracted, unrounded, front open vowel. To achieve this sound, think about cupping the tongue and retracting the root of the tongue.