In a large zip-top bag, toss together 1/2 cup cornstarch, baking soda, salt and pepper. Add beef and give it a shake to coat.
In a large skillet, heat the oil over medium-high heat. Sear the beef for about 1 to 2 minutes on both sides and add to slow cooker.
In a medium bowl, whisk together the soy sauce, broth, sugar, hoisin sauce, chili sauce, chili flakes, garlic and ginger until dissolved and pour over the beef.
Cover and cook on LOW for about 3 to 4 hours.
About 30 minutes prior to serving, whisk together remaining cornstarch with water in a small bowl and stir into the slow cooker along with the carrots, pineapples, and pineapple juice.
Cover with lid, turn heat to HIGH and allow the sauce to cook and thicken up for about 20 to 30 minutes.
Serve over rice and garnish with green onions and sesame seeds, if desired.