You can't get to your right side on your backswing and the resulting reverse pivot causes you to consistently slice the ball.
\nWhy it happens
You have too much weight on your left side at setup because your hips are tilted the wrong way.
What to do
\n At address, your hips should be level. Level hips allow you to make a balanced swing and, importantly, position your right hip to accept weight and load up behind the ball for a power-rich downswing and impact. This change will make a positive impact on your swing immediately.
\n The Fix
\nAddress your ball and then use your hands to adjust your hips into a level position (use your belt as a guide). For even greater power and to really lessen the chance of a reverse pivot, push your right hip down below your left. This allows you to accept even more weight on the backswing and ratchet up the energy of your swing.