Add salt, pepper, soy sauce, ketchup, agave, garlic, ginger, Sriracha, and lime juice to your slow cooker. Whisk to combine.
Place chicken breasts in the slow cooker, turning to coat in the sauce.
Cover and cook. For boneless chicken, cook on low for 5 hours or on high for 3 hours total. For bone-in chicken, cook on low for 6 hours or on high for 4 hours total.
When the sauce is simmering in the last hour of cooking time, whisk the cornstarch and water together in a small bowl until the cornstarch is dissolved. Stir the cornstarch mixture into the sauce in the slow cooker. Cover and cook remaining hour to allow the sauce to thicken.