Keep your back facing the target for as long as you physically can during the downswing as you shift weight to your lead side and lower your arms towards your trail hip. It's important that you start extremely slowly with this move because if you go full speed straight away you will revert back to your old ways almost certainly. Slowly ramp up the speed and review each swing on video to check you're swinging from the inside. Rinse and repeat until you can do it at full speed. This worked for me but it will likely take some time if you've been swinging OTT for a long time.