Spray your slow cooker with nonstick spray.
Place the chicken breasts in the bottom of the slow cooker. Add the broccoli on top.
In a medium bowl, whisk together the chicken broth, soy sauce, maple syrup, sesame oil, salt, pepper, garlic, ginger, and onion flakes. Pour the mixture over the chicken and broccoli.
Cover and cook on high for 3 hours (or low for 5–6 hours). For crisper broccoli, add it during the last 30 minutes of cooking.
In a small bowl, whisk the cornstarch with water to form a slurry. Stir this mixture into the slow cooker and cook for an additional 5–10 minutes, or until the sauce has thickened.
Serve over rice, sprinkle with sesame seeds, and enjoy.