The banana-ball slice almost always comes from one move: the club coming 'over the top' and cutting across the ball. You can feel it and fix it yourself with a few range drills.
A slice is side-spin from the club moving left of the target (for a righty) while the face points right of that path. The usual cause is the arms throwing the club 'over the top' from the top of the swing, sending it out-to-in across the ball. Fix the path and the slice shrinks fast — no swing rebuild needed.
Before touching your swing, check your aim. Slicers often unconsciously aim further and further left to allow for the curve, which steepens the over-the-top move and makes the slice worse — a vicious loop. Set your feet, hips, and shoulders parallel to the target line, play the ball off your lead heel with the driver, and let your trail shoulder sit slightly lower at address. A neutral setup removes half the reasons to come over the top.
If your slice sends it right, exaggerate the opposite feel: swing as if hitting the ball toward right field (for a righty), letting the club drop to the inside on the way down. It'll feel wrong — like you'll hook it — which is exactly the point. Most slicers need a big feel to make a small real change.
The over-the-top move usually starts with the upper body and arms lunging first from the top, throwing the club steeply out and over the plane. The antidote is sequence: start the downswing from the ground up — a small pressure shift into your lead foot — so the club drops to the inside instead of being flung outward. Feel your trail elbow tuck toward your side on the way down rather than pushing out toward the ball.
Two that work: (1) place a headcover just outside and behind the ball — swing without hitting it, forcing an inside path; (2) tee the ball and try to hit gentle draws to the range's right side. Do these slowly at half speed first; grooving the new path matters more than smashing it.
Some slicers fix their path but still slice because they "hold off" the face out of fear of hooking, leaving it open at impact. Let the club release: feel your forearms rotate through the ball so the toe of the club passes the heel and the face squares up. Combined with an inside path, a free release is what turns the weak fade into a straight ball or a gentle draw.
A weak grip (hands rotated too far left) props the face open and guarantees slice spin even with a decent path. Rotate both hands slightly right until you see two or three knuckles on your lead hand. Often a small grip fix plus the inside-path feel straightens the ball more than any single 'tip.'
New moves collapse under pressure, so bridge the gap deliberately. Groove the drills at half speed, then hit shots at three-quarter tempo before ever swinging full-out. On the course, don't chase a perfect draw — pick a single swing thought (one clear feel, like "trail elbow down") and commit to it. Expecting some slice while the change beds in keeps you from snapping back to the old over-the-top lunge.
Watch for these while you're grooving the fix — they quietly reintroduce the slice: