Place the chicken legs in the bottom of a 6-quart slow cooker in a single layer or slightly overlapped.
In a medium bowl, whisk together the peach preserves, minced garlic, ketchup, soy sauce, ground ginger, and crushed red pepper flakes until smooth and combined.
Pour the sauce evenly over the chicken legs, turning pieces to coat if needed.
Cover and cook on LOW for 5–6 hours, or on HIGH for 4 hours, until the chicken is cooked through and tender.
Remove chicken from the slow cooker and spoon sauce over the top before serving.