Heat oil in a large saucepan on high. Fry chicken 8-10 minutes, turning till browned. Transfer to plate.
Reduce heat, sauté celery, onion, carrots and garlic for 4-5 minutes. Stir in cumin, coriander, chilli & ginger. Cook 1 minute.
Poor stock into the slow cooker along with tomatoes, lentils, beans and chicken. Transfer veggies to slow cooker, stir all ingredients together and cook on high for 2-3 hours. (Depending on the heat of your slow cooker).
Remove chicken legs and remove meat from bones & shred a little, return the meat to the ingredients. Add rice, stir and leave cook for another 1 hour or until thicken to your liking. (If it gets too thick, just add some water).
Stir in lemon juice if using it.
Serve topped with coriander leaves if using.