Pre-heat oven to 220ºC.
Peel and quarter potatoes.
Add potatoes to salted cold water in a large pan. Bring pan to a rolling boil.
Cook for 5 minutes, remove from heat and drain thoroughly.
Return drained potatoes to the empty pan. Shake vigorously.
Mix cornmeal, salt, pepper, and thyme in a large mixing bowl.
Add oil to a roasting pan and bring up to temperature in pre-heated oven.
Toss potatoes in coating mixture then add to the hot roasting pan.
Mist lightly with spray oil.
Note: if using air fryer, set to Roast function for half an hour. Halfway through roasting, turn the potatoes gently. After half an hour, check to see if they need a little longer and cook for 5 minute increments if needed until done.
Oven cook: roast for 20 minutes, turn potatoes in roasting dish. Add some red onion at this point if desired. Cook for an additional 15 minutes.
Serve while hot and crispy.