There’s a lot more to deep-frying than just flour and oil. Yes, you need both, but throw a few more ingredients into the process and you’re golden.
Fish filets or thinly sliced chicken breasts work best. Or you can cut them up and make “fingers.” Three bowls contain all you need for the batter: one with flour, one with egg whites and one with some kind of breading, like bread crumbs or even Ritz crackers. I don’t know what it is about this mixture that works so well, but whatever you deep fry will come out a lot nicer than if you just use one of these ingredients.