Preheat the oven to 325 degrees F (165 degrees C).
Coat the chuck roast with garlic salt, pepper and mustard powder. Heat the oil in a large oven-proof skillet or Dutch oven over medium-high heat. Add the roast and brown on both sides, about 5 minutes per side.
In a medium bowl, stir together 3 cups of water, soy sauce, vinegar, honey, ginger and celery seed. Pour over the roast and then cover the roast tightly with a lid or aluminum foil.
Bake in the preheated oven until the roast is very tender, 2 1/2 to 3 hours.
When the roast is done, remove it from the pan to a serving plate. Set the pan of drippings over medium-high heat and bring to a boil. Stir together cornstarch and 1/4 cup of cold water. Pour into the boiling liquid and stir until thickened, about 1 minute. Serve the roast with the gravy poured over.