In a medium bowl, combine the chicken, 1/2 tsp baking soda, salt to taste, 2 tbsp fresh orange juice, 1 1/2 tbsp soy sauce, 1/2 tsp black pepper, 1 tbsp cornstarch, 1 tsp minced garlic, and 1 tsp minced ginger; mix well to coat and marinate for at least 10 minutes.
In a separate bowl, whisk together 1/3 cup fresh orange juice, 1 tbsp soy sauce, 1/4 cup rice vinegar, 1 1/2 tbsp chili garlic sauce (optional), 1/2 tbsp cornstarch, 2 tsp orange zest, 3 minced garlic cloves, 1 tsp minced ginger, 1/2 tsp red chili flakes, 3 tbsp brown sugar, and salt to taste until the sugar dissolves; set the sauce aside.
Heat 1 tbsp oil in a wide skillet over medium heat until shimmering.
Add the marinated chicken to the skillet in a single layer and cook 4–5 minutes without moving until the underside is browned.
Flip the chicken pieces and cook another 5–6 minutes until cooked through and no longer pink in the center.
Pour the prepared sauce into the skillet, stir to combine, and cook uncovered for about 5 minutes until the sauce thickens and coats the chicken.
Stir in 1 tbsp sesame seeds and 2 tbsp chopped green onions, then remove from heat.
Serve the orange chicken over cooked rice with steamed broccoli on the side.