Allowing your dog to mix with your chickens is not something to take lightly. A lot rests on the early introductions and also some luck with your dogs natural temperament. A flock of chickens will usually run off in all directions if a dog (particularly one they are not used to) comes bounding over to them and that can easily start a game of chase. If the first time your dog meets your chickens it has a great time chasing them it will be harder to persuade your dog in the future that they are not just a fun game. Sadly for the chickens it is far from fun and can easily turn deadly.
First introductions can start with chicks. In Tyler Edwards video below they explain how they introduced their dog to their chickens as chicks and got her used to them as they grew. They were never left alone together. Once grown and placed outside they were again carefully introduced under supervision.