Maybe you cut it too thick, so you must cut it as thin as possible for dry frying. Another key is that you haven't cooked it yet, and it should be almost golden brown when frying it. It will take a long time, so don't catch it in a hurry. After the shredded potatoes are cut and rinsed with water, you don't need to add starch. If you want to add it, you should use raw flour, not too much. I never add any flour, which is absolutely crisp. You can try.