Heat oven to 400F/200C and lightly grease a baking tray with oil.
Thickly spiralise the sweet potatoes, or alternatively cut into thin strips.
In a large bowl, gently toss the sweet potato with the cornflour. Add the oil and toss to coat.
Spread it all onto the baking tray or cooking mesh, taking care not to overcrowd it or the results won’t be crispy. Use another baking tray if necessary.
Bake for 20 minutes, turning the sweet potatoes halfway through and turning the trays. They will continue to crisp up after they come out of the oven.
Serve hot, seasoned with salt and pepper.
Notes
Toss them in cornflour (cornstarch) to absorb the moisture.
Don't crowd them on the pan or they'll steam rather than bake.
For best results, use a cooking mesh, although a hot baking tray will work well too.
If spiralizing, make them thick as they'll shrink when cooking.
Make sure the oven is hot before cooking them.
They will continue to crisp up when out of the oven, so don't cook them too dark.