Preheat the oven to 450 degrees F (235 degrees C).
Bring a large pot of water to a boil, and boil potatoes until tender, 8 to 10 minutes; drain.
Transfer potatoes to a large bowl. Drizzle with oil, season with 1 tablespoon taco seasoning and salt. Toss until well combined. Spread potatoes evenly onto a rimmed baking sheet.
Bake in the preheated oven until crispy and golden brown, about 20 minutes. Reduce oven temperature to 400 degrees F (200 degrees C).
Heat a large skillet over medium-high heat. Cook and stir ground beef in the hot skillet until browned and crumbly, 5 to 7 minutes. Season with remaining taco seasoning. Drain grease if needed.
Transfer potatoes to a 8x10-inch casserole dish. Drizzle with half the nacho cheese, then add ground beef on top. Sprinkle with Cheddar and drizzle with 1 to 2 tablespoons taco sauce.
Bake in the preheated oven until cheese is melted and bubbly, about 20 minutes.
Top with sour cream, remaining nacho cheese and serve immediately.
