Feet wider than shoulder width apart, externally rotate at the hips turning feet out at a 45-60 degree angle, soft bend in knees, abs/glutes engaged, shoulders back, neck neutral.
Dumbbell Sumo Squat:
Starting from the exercise posture stance with the feet wider than shuolder width and turned out at the 45 to 60 degree angle, begin the movement by pushing the butt back as if you were to sit in a chair. Slowly bending your knees and lowering your hips to the ground until quads(top of thigh) is parallel to the floor. You will feel a stretch in the adductors(inner thigh) as you lower the the bottom of the movement. Start to engage the glutes and and drive through the heels pushing off the ground to get back into the beginning stance.
Common errors include rounding the back/shoulders, letting the knees buckle(knee valgus), initiating the movement from the knees and not the hips, shifting into the toes and not keeping weight through heels.