You can diagnose your own swing by going through a checklist. If you are slicing, you can check the "Downswing Step 1" section to see if your hips are clearing before your arms move.
Instead of a closed fist, use an open-palm strike targeting the opponent’s nose or chin. simple strike sequence pdf
Set up to the ball with your feet completely together. As you take the club back, take a step forward with your lead foot just before the club reaches the top of the backswing. Hit the ball from this moving position. This drill physically forces you to initiate the downswing with your lower body. The Alignment Stick Impact Drill (Prevents Flipping) You can diagnose your own swing by going through a checklist