Steep the saffron in 60ml hot water for 5 minutes. Heat the oil in a frying pan and sear the chicken thighs for a couple of minutes until golden. Transfer to the slow cooker. Add the steeped saffron and all the remaining ingredients, except the fresh herbs. Stir well. Cover and cook on high for 1 hour, then turn down to low and cook for a further 3 hours.
Remove the lid, season and stir through the fresh herbs. Serve with flatbreads.