Using a baking tray , place the oven proof bag onto the baking tray , spread out in the bag on the tray , so they cook evenly , and place the baking tray into the oven and cook for 30 minutes , until they feel quite tender , after the 30 minutes , remove the chicken pieces from the baking tray and drizzle the oil onto the hot baking tray , then open the chicken filled bag , discard bag and place the chicken pieces , spread out , onto the oiled baking tray and place the baking tray back into the oven and cook for a further 10-15 minutes or until cooked through golden tender .