from the corner of your mouth quickly to the sides

We do it fast because it's a short vowel and we level our hands with our mouth to better connect lips and hands movements.

Place your hands on either side of your mouth, palms up, straight, then move them with a jerk to the sides, opening the space between them. The movement of the hands, sideways, reflects that our lips go back as in a smile, but the mouth is much more open than when we pronounce TEA (a vowel with a motion also moving sideways but closed)