Come up with the system for judging distance on those shots. Work on your bunker game, doing your drills and playing different length shots to get a feel for distance. Most amateurs do their practicing in after-works session. Actually the best time to practice is after a round, as the professionals do. That way you can work on the problem areas that cropped on during the round.
Slices result from an open clubface at impact.
This usually occurs due to insufficient rotation of the hands and arms on the downswing. At impact, the club head lags behind the hands and arms and the clubface is left open, imparting sidespin on the ball that causes it to curve from left to right. The following drill will improve your hand action and enable you to square the clubface at impact. Using a wedge and teeing the ball so it is easier to hit solidly, hit a series of shots making half swings. Swing slowly and try to feel your hands and arms rotating the club into a square position through impact.