Prepare the Marinade: In a bowl combine soy sauce, grated ginger, garlic, and cornstarch, whisking until smooth. Marinate fish for 15 minutes to soak up flavors.

Heat the Wok: Warm oil in a wok over high heat until shimmering (around 400°F), creating a searing surface that cooks fish quickly to maintain tender texture.

Sear the Fish: Add fish fillets in a single layer; cook 2 minutes per side until edges turn opaque and lightly golden. Remove and set aside.

Stir-Fry Vegetables: In the same wok, add bell peppers, snap peas, and carrots, stirring for 3–4 minutes until crisp-tender.

Add the Sauce: Lower heat to medium; stir in oyster sauce, rice vinegar, brown sugar, and chili flakes. Cook 1 minute until sugar dissolves.

Combine and Finish: Return fish to the wok, drizzle sesame oil, and gently toss for 30 seconds until everything is well coated and heated through.