Cut potatoes into chunks and boil in salted water until soft.
Drain well and let cool slightly.
Place potatoes in a bowl and add flour, cornstarch, chili flakes, cumin, pepper, salt, and coriander.
Mash and knead into a soft dough.
Flatten the dough into a rectangle on parchment paper.
Cut into even sticks with a knife.
Heat oil in a deep pan over medium heat.
Fry the sticks in batches until golden and crisp.
Drain on paper towels and serve hot.
Tip: Keep oil at medium heat so the fingers cook through without burning.