In a large bowl, combine the cornstarch, flour, salt, black pepper, garlic powder, and onion powder. Toss the sliced flank steak in the mixture until well coated.

Heat the vegetable oil in a large skillet or wok over medium-high heat. Once hot, add the coated beef in batches, ensuring not to overcrowd the pan. Fry for about 2-3 minutes on each side until golden brown and crispy. Remove and drain on paper towels.

In the same skillet, remove excess oil, leaving about 1 tablespoon. Add the minced garlic and ginger, sautéing for about 30 seconds until fragrant.

Pour in the soy sauce, brown sugar, rice vinegar, chili paste, and sesame oil. Stir well and bring to a simmer.

Add the sliced bell peppers and cook for an additional 2-3 minutes until slightly softened.

Return the crispy beef to the skillet, tossing to coat it in the sauce. Add the sliced green onions and stir for another minute.

Serve immediately over steamed rice or noodles.