Pat the chicken dry and season lightly with salt, pepper, smoked paprika, and onion powder. Place the pieces in the bottom of the crock pot in a single layer if possible.
In a medium bowl, whisk together the maple syrup, Dijon mustard, soy sauce, apple cider vinegar, minced garlic, and red pepper flakes (if using) until smooth.
Pour the sauce evenly over the chicken. Cover and cook on LOW for 4–6 hours or HIGH for 2–3 hours, until the chicken is tender and reaches 165°F (74°C).
Remove the chicken and transfer the cooking liquid to a saucepan. Simmer to reduce and thicken, or whisk in a cornstarch slurry (1 tsp cornstarch + 1 tsp cold water) until glossy. Return sauce to the chicken or spoon over when serving.
Serve the chicken over rice, mashed potatoes, or alongside roasted vegetables. Garnish with chopped parsley or chives.
Notes
For more forgiving results, use chicken thighs rather than breasts.
To make a one-pot meal, add hearty vegetables like carrots and potatoes to the crock pot before cooking.
Store leftovers in an airtight container for up to 3 days.