If you are struggling with a steep swing plane in your transition, you may want to try practicing with the ball above your feet.
As demonstrated above by Swing-U instructor Ryan Rustand, this can help you to naturally shallow out your swing plane. When practicing this be sure to use a club that is not too long as the ball will be higher and closer to your body when you set up.
When performing this drill, notice how the club works more around your body rather than up and down. Take the same motions you are using in this drill and apply them to your actual golf swing.