The crossback squat progression works on strength in your hips in a bit of internal rotation - you may feel this in your outer glute more than other squats, and you might have to play around with positioning to get this just right. Make sure there's no uncomfortable twisting or sharp feelings in your knees. For the open chain variation, cross one leg behind the other and sink downward, sending your front knee forward, then drive back outward, bringing your back leg back to the starting point. Either alternate or complete all reps on the same side.