Preheat oven to 350 degrees F (175 degrees C). Lightly grease a medium baking dish.
Season chicken with garlic salt. Arrange in the prepared baking dish. Bake 45 minutes in the preheated oven, until no longer pink and juices run clear. Cool, shred, and set aside.
With metal tongs, char each tortilla half over the open flame of a gas stove burner for about 1 minute, until lightly puffed.
Pour about 1/2 inch enchilada sauce in the bottom of a medium baking dish, and arrange 6 tortillas in a single layer. Top with 1/2 the chicken, 1/3 cheese, 1/2 the sour cream, and 1/3 of the remaining enchilada sauce. Repeat. Coat remaining tortillas thoroughly with remaining enchilada sauce, and arrange on top of the layers. Sprinkle with remaining cheese, and top with any remaining enchilada sauce
Cover, and bake 45 minutes in the preheated oven. Cool slightly before serving