In a mixing bowl, combine the chicken pieces with soy sauce, oyster sauce, black pepper, and salt. Stir well, ensuring each piece is evenly coated. Set aside to allow the flavors to infuse. In a separate large bowl or a resealable plastic bag, add the cornstarch and set aside for later use.

In a medium-sized bowl, whisk together the oyster sauce, soy sauce, black pepper, minced garlic, grated ginger, chicken stock, sugar, and cornstarch. Stir until the sugar and cornstarch are fully dissolved, creating a smooth, flavorful sauce.

Remove the marinated chicken from the bowl and transfer it into the prepared cornstarch mixture. Toss thoroughly until each piece is well-coated, creating a light, crispy outer layer that will enhance the texture when cooked.

Heat a large skillet or wok over medium-high heat and pour in the vegetable oil. Once the oil is shimmering, add half of the chicken pieces, ensuring they are spaced apart to allow even browning. Cook for approximately 5 minutes, flipping halfway through, until the chicken develops a golden, crispy exterior and is cooked through. Transfer to a plate, keeping the remaining oil in the pan. Repeat with the remaining chicken, adding more oil if necessary.

If needed, add a small amount of oil to the same pan before tossing in the onion, celery, and red bell pepper. Sauté over medium-high heat, stirring occasionally, until the vegetables become tender but still retain a slight crunch, enhancing the dish with their vibrant texture.

Pour the prepared sauce into the pan and let it simmer, stirring occasionally, until it thickens slightly. Add the crispy chicken pieces back into the skillet and toss them in the sauce, ensuring every bite is coated in the bold black pepper glaze.

Spoon the black pepper chicken over a bed of hot, steamed white rice, allowing the savory sauce to soak into the grains. Serve immediately for a flavorful and satisfying meal.