Got an ugly squat? Then you need to get better at squatting lighter loads. Learn to control your squat. “Butt wink” (posterior pelvic tilt) arises because most people are flat-out unstable and aren’t used to squatting to depth. They lack ample stability and motor control within that range of motion.
This is one of the many reasons why goblet squats are so valuable. You can groove a rock-solid squat pattern – sit back, push the knees out, keep the chest tall, and more importantly, learn to brace the abs harder. In this video, one of my athletes with the butt wink problem slows things down and forces himself to control his squat and own his position.
Goblet squats make it easier to slow things down. Implement a lot of controlled slow-eccentric squats to force yourself to stabilize and to still keep time under tension high.