Slices can have multiple root causes, but the answer is simple: The face points to the right of the path (for a right hand golfer) at impact.
Causes can be:
1: A grip that is too weak causing the face to point to the right.
2: An outside in swing path
3: Poor hand/wrist action which open the face through impact
Corrections are to make sure the grip is aligned correctly. Learn to swing on the correct path (This is tricky and involves posture that tilts away from the target, hips leading the swing, not arms). Keeping the right hand on top (or rotating over) through impact.