Any potato that roasts well works here. I recommend Russets or Yukon Golds in the US, Maris Piper or King Edward in the UK, or Dutch Cream in Australia.
For the frying method, use a high smoke point oil such as corn, peanut, grapeseed, or vegetable oil.
Do not overcrowd the baking sheet; potatoes will steam instead of crisping.
For extra crispiness, turn the potatoes halfway through the baking time.
Adjust the heat by varying chili flakes to your taste, or substitute fresh minced chili, cayenne powder, or chili powder.