I think this has been mentioned, but, yes, first of all position yourself for the return by standing farther to the left. Then move in toward the ball, to cut off the angle as much as possible. Also, as mentioned, especially if there is a lot of hop/spin to the ball, you need to make square contact and drive down and through the ball.
In general, when hitting a slice return like this, the idea is to drop the ball low to the feet of the server who would be approaching he net forcing him to volley (or half-volley) up where your partner waits at the net.
When you are pulled wide like that, and with the opponent waiting at the net, your angle for making your slice return work is very slim. If it is not over enough, or if it floats too high, the net man will take it and pound back a winning placement.
So, have someone hit you serve after serve, wide in the ad court for practice until you get it down.
Until you do, there are, also, some other shots you might consider.
a, A topspin drive down the line (every once in a while to keep the net man on his toes).
b, A heavy topspin crosscourt that dips down-- allowing you to hit harder and create more angle.
c, A lob over the head of the net man.