The bracing sequence of butt then abs is extremely important. This helps stabilize both the back and the knees once you begin moving. After bracing, shift the weight to one foot and keep both the back and head in neutral as you push your hips back. The shins should be kept as upright as possible while pulling the hips back and dropping. Go only so far as you can control your back from rounding and knee from caving in. Both of those are signs that we need to decrease the depth and work on the movement pattern and strength. To return upright, drive through the foot while bringing the shin back to perpendicular and reset.