Cover and cook on low for 3-4 hours on low (see notes) or until the turkey has reached an internal temperature of 165 degrees. For a really juicy turkey, take it out around 160 degrees since it will continue to cook as it rests. Bone-in turkey breasts will take closer to 6 hours. Let rest for 15 minutes before slicing or serving.
For crispy skin: Preheat the broiler to high heat and the baking rack about 10-12 inches from the heat source. Place the turkey on a sheet pan covered with foil. Broil for 3-5 minutes until skin is browned and crispy. Keep a close eye so it doesn't burn.
Optional gravy: Melt 2 tablespoons of butter over medium heat in a pot. Once melted, add 2 tablespoons of flour to make a roux. Whisk together and cook for 1-2 minutes until flour is fully incorporated and light brown in color. Add 1 cup of the strained cooking liquid from the slow cooker. Continue to whisk and cook until it thickens. This normally takes about 5 minutes. Taste and season as needed.