In a bowl, add the sesame oil, tapioca flour, garlic, ginger, cumin, cinnamon, and black pepper and stir to combine.

Add the flank steak and toss to cover the meat with the marinade. Marinate at room temperature for at least 15 minutes.

Transfer the flank steak to a 4- to 6-quart slow cooker.

Add the water, coconut aminos, and brown monk fruit sweetener. Add the edamame or broccoli, if using. Cover and cook on LOW for 4 hours, until the steak is cooked through and tender.

Garnish with the green onions and sesame seeds.