Forum member Laura sized up on an Ann Taylor pair and they are slouchy for her.
Forum member Shannon sized up and TAPERED a Lord and Taylor pair.
Forum member Sveta also tapered a pair of regular trousers, sized up somewhat (I believe).
I found slouchy trousers at Winners (like TJ Maxx).
But I haven't seen many in chain stores except for Zara. They have quite a lot of different versions.
I tried the "size up with regular trousers" and the look didn't quite work on me. I am not sure why - whether I just didn't have the right pants, or what. Actually, if I recall, I was trying this with jeans for a slouchy skinny look, and it just didn't work with the styles I tried. But it can and does work with some jeans on some bodies.