One thing you can try is to set up with a spine tilt away from the ball. What this does is to alter the normal alignment between the shoulders and the hips (the shoulders are further back behind the ball). Part of what is happening when you slide the hips to the left is the creation of this tilt at impact, and it's not a bad thing to get the hips 'ahead' of the shoulders (through the tilt).

Try hitting some balls with a slightly exaggerated tilt on the practice ground. To do this, slide the hips to the left at set up so that more of your natural weight is on the left side, tilt the spine to get your shoulders back. When you do this, you should feel the left side acting as more of a brace - after all, there's a limit to how far the hips can go left if the rest of the body doesn't follow. Now, hit some balls from this starting position. You will now not be able to slide any more to the left on the downswing.; see what happens......