Cut the chicken into bite-sized ½ inch pieces and place them in a large bowl. Sprinkle the flour, corn starch, salt, black pepper, onion powder, paprika, and ginger powder over the chicken and toss everything until all pieces are evenly coated.
Heat vegetable oil in a deep pan over medium-high heat until shimmering. Fry the coated chicken pieces for about 2 to 3 minutes, turning occasionally, until each piece is golden and crispy but not overcooked to avoid toughness.
While frying, whisk together fresh orange juice, corn starch, vegetable oil, soy sauce, vinegar, brown sugar, ginger, garlic, black pepper, orange zest, and optional chili flakes in a bowl. Pour this mixture into a hot non-stick skillet and simmer on low heat, stirring regularly until the sauce thickens.
Add the fried chicken to the thickened sauce and stir well to ensure every piece is nicely coated. Let everything simmer together gently for another 1 to 2 minutes to combine flavors, then remove from the heat.
Serve the saucy orange chicken with homemade Lo Mein noodles or steamed white rice. Optionally, top with toasted sesame seeds and chopped green onions to enhance the presentation.
