Preheat oven to 425 degrees F. Line a baking sheet with parchment paper.
Cut the potatoes: wash and scrub potatoes. Cut lengthwise into 4 to 6 wedges each, about 3/4 inch thick at the widest point.
Mix seasonings: combine cornstarch, salt, pepper, garlic powder, onion powder, paprika, thyme, and cayenne in a large bowl.
Coat the wedges: add potatoes to the bowl, pour oil over top. Toss until evenly coated. Let sit 5 minutes.
Arrange on pan: spread wedges in a single layer with space between each. Do not crowd.
Bake: bake 35 to 40 minutes, flipping halfway, until golden and crispy outside and tender inside.
Rest and serve: let rest 2 to 3 minutes. Garnish with parsley. Serve with dipping sauce.