Peel and quarter the onions. Peel and chop the carrots. Place them in the bottom of your slow cooker pot.
Crush the garlic cloves and add to the bottom of the slow cooker.
Combine together the herbs, spices and lemon juice to make a rub. Then apply this to the skin of the chicken, ensuring your cover the whole surface.
Place the chicken on top of the prepared vegetables. Turn your slow cooker onto high for at least 30 minutes.
There is no need to add any liquid, as the chicken will produce its own juices.
Once the slow cooker is warmed up either slow cook on low for 12 hours or slow cook on high for around 5-6 hours. Check that the juices run clear and the meat is no longer pink before serving.