I used to have this problem as well. I would have to aim as far to the left as possible without being in trouble if I accidentally hit it straight. That was back when I was a 20 handicap. Since then I have dropped to a 5 (would be lower if i could putt). What i have done is a combination of a few easy things i suggest trying 1 at a time and in varying degrees before combining them as you don't want to go from 1 extreme to another.
1) Option 1: Take your normal stance and address the ball. Now take your front foot (nearest the target) and move it forward (towards the ball). Take your normal swing. This will feel awkward, but it helps to influence a Draw and therefore will lessen the slice.
2) Option 2: Grip the Club as normal and address the ball. Now take your lower hand and roll it away from your target so your palm faces up to the sky. This will make you flip your wrists more and encourage a draw, again will help lessen a slice.
3) Option 3: Take your normal stance. Now take a small step back away from the ball (0.5" -1" at a time). Swing normal. Moving back will hopefully cause you to hit the ball a little more on the Toe of the club with should draw the ball. (it will also allow you to fully extend your arms and may gain you some distance).
4) Option 4: If in your normal stance, while at address, there is an angel between your arms and the shaft of the club (i.e. your arms are more pointed to the ground while the shaft of the club is pointed at the ball) try raising your arms so that your arms and the shaft are in a straighter line pointing down to the ball. This should help create a draw.
5) Option 5: My last suggestion is only if you can't manage to do it any other way, but you can always purchase a club that has a closed face. I am against this because it makes it difficult to switch clubs later, or if you do end up fixing your swing the club will become just as big a problem creating a hook.
Using a small combination of these tips has made me move to a club that is actually 2* open and hitting it further than most people i play with.
Hopefully one of these (or a combination) tips will help straighten out your ball flight as well. Good luck. see you at the 19th hole.