In a bowl, mix the oregano, salt and pepper. Rub the mixture into chicken. Melt the butter in a frying pan over medium heat. Brown chicken in butter for 3 to 5 minutes on each side. Place chicken in a slow cooker.
In the same frying pan, mix the water, lemon juice, garlic, and stock paste. Bring the mixture to the boil. Pour over the chicken in the slow cooker.
Cover, and cook on High for 3 hours, or Low for 6 hours. Add the parsley to the slow cooker 15 to 30 minutes before the end of the cook time.