Heat the nonstick skillet over medium-high heat. Add the chicken and sauté until lightly browned, about 8 minutes. Transfer the chicken from the pan to the slow cooker, reserving any drippings. Add the onion to pan and sauté until just soft, about 3 minutes. Add the ginger, curry powder, coriander, cumin, red pepper, and garlic. Sauté for 2 minutes. Pour the onion mixture over the chicken in the slow cooker. Stir in the sweet potato, kosher salt, tomatoes, bay leaves, and cinnamon stick.
Cover and cook on low for 6 hours. Discard the bay leaves and cinnamon stick. Turn the slow cooker off and let stand for 15 minutes. Stir in the yogurt. Serve over rice with cilantro garnish.