You know, at the beginning of the forward/downward swing the racket face is open, right?If anything, I think you need to lean forward a little, which will let you hit it more in front. I can't tell for sure from this angle, but you might be doing what I used to, which is to flex the wrist while making the stroke (before contact). Maybe that is what leads you to open the racquet face too soon. You keep the wrist steady and don't move the elbow either. With both these parts static, now try to get the racquet from a slice takeback and finish with a slice follow through. That's how it should be hit. It will initially be difficult to time the shot this way but with repetition, you will get used to it.
So there are two possibilities to explain the floaters:
1. Contact point too far in front
2. I cannot close the racket face soon enough due to lack of supination/external shoulder rotation before contact.