Mold grated potato into a patty shape. Season with salt. Heat oil in a skillet over medium-low heat. Cook potato patty until browned on both sides, about 5 minutes. Set aside. Heat another skillet over medium-high heat. Cook and stir sausage in the hot skillet until browned and crumbly, 5 to 7 minutes. Set sausage aside on a plate, reserving grease in the skillet. Heat reserved sausage grease over medium-high heat. Add onion and bell pepper and saute until softened, 3 to 5 minutes. Transfer to a bowl and set aside. Heat the same skillet over medium-high heat. Whisk egg in a bowl and pour into the skillet; cook and stir until set, about 5 minutes. Pour gravy mix into a small saucepan. Whisk in water. Cook over medium heat, stirring frequently, until gravy comes to a boil. Reduce heat and simmer for 1 minute. Remove from heat; gravy will thicken upon standing. Place cooked hash brown potato patty in the bottom of a serving bowl. Top with egg, sausage, onion and pepper mixture, and gravy, in that order.