How can I level my basement floor, which has a 2-3inch dip in the middle?
If there isn’t a moisture problem, I’d use a gypcrete self-leveling compound. Feather to edges and cover entire floor with your final floor finish. (Gypcrete can’t be left exposed. It’s not a walking surface.)
Gypcrete can only be installed to 3”-4” depth, so it would be fine. If there’s a moisture problem, you must take care of that first.