I try to remember to cock my left shoulder in a little bit before I start my back swing. It's something I started doing at the end of last year and I started finding it reduced my slice immensely. I read that you tend to swing in the direction your shoulders are lined up with and I think they were too open at address. It seems to give me a better turn on the way back too.
I have the same issue. According to my pro, getting the shoulders too open with the woods, is a common problem and certainly exacerbates any fade/slice.