Combine cornstarch, sugar, soy sauce, and broth in a small bowl. Whisk until smooth. Stir in ginger, toss in beef and stir to coat. Heat 1 tablespoon of vegetable oil over medium heat.
Cook the roast uncovered in a shallow baking dish for 24 hours. Cook at 250 degrees for the first hour. Cook at 150 degrees for the next 22-1/2 hours, and cook at 250 degrees for the last half hour before serving.