Mix soy sauce, oyster sauce, hoisin sauce, and broth.
Mix cornstarch with 2 tbsp water, set aside.
Heat oil in a wok on medium-high heat.
Cook shrimp for 2 minutes, then remove.
Cook chicken until golden, then remove.
Cook beef until browned, then remove.
Add garlic, ginger, and red pepper flakes.
Stir-fry vegetables for 3 minutes.
Add shrimp, chicken, and beef back to the wok.
Pour sauce over everything and mix well.
Add cornstarch mix to make the sauce thick.
Cook for 2 more minutes and serve hot.