Bear in mind that self levelling is not auto-magically self levelling. It flows so that it should level itself but it's easy enough for that to not work. You are expected to rub it down to perfectly flat.
This main struggle I have with it is estimating the required quantities. It's also difficult to do the entire floor in one go although that would seem like technically the best approach. I've not used it very often though.
Bear in mind that self levelling is not auto-magically self levelling. It flows so that it should level itself but it's easy enough for that to not work. You are expected to rub it down to perfectly flat.