Boil the noodles: Bring a large pot of water to a boil. Cook the noodles until very al dente. Drain and rinse with cold water to stop the cooking process.
Make the sauce: In a medium bowl, whisk the soy sauce, oyster sauce, sesame oil, and water until well combined.
Prep the chicken: In a medium bowl, combine the chicken with 1½ tablespoons of the sauce, the cornstarch, and salt. Stir until the chicken is evenly coated.
Heat 1½ tablespoons of the oil in a nonstick skillet over medium-high heat until shimmering. Add the chicken and cook, stirring frequently, until just cooked through, about 3 minutes. Transfer the chicken to a plate.
Add the remaining ¼ cup of oil to the skillet, then add the cabbage, celery, carrots, scallions, and garlic. Cook, stirring frequently, until softened and starting to brown, about 8 minutes.
Add the noodles, chicken, and sauce, and stir-fry for about one minute, until well combined and the noodles have absorbed the sauce. Taste and adjust seasoning, if necessary. Serve.