Slow roast a turkey by seasoning it ahead of time and cooking it at 170 degrees Fahrenheit for an hour for each pound of the bird. You can also cook it at 250 degrees for 20 minutes per pound.
To slow roast a turkey, start the process at least 48 hours before you want to serve it. Rub salt and pepper to taste over and under the skin as well as inside the turkey. Chill the turkey uncovered between 12 and 24 hours. Rub oil over the skin of the turkey, and roast it at 450 degrees Fahrenheit for 45 to 60 minutes, just long enough to kill bacteria and turn the outside a deep golden brown. Pour apple cider over the turkey, and season it with seasoning of your choice such as poultry spice.
Return the turkey to the oven, and slow roast at 170 degrees Fahrenheit for one hour per pound. A 20-pound bird requires 20 hours of slow roasting. If you opt to cook it at 250 degrees Fahrenheit, only brown it at 475 degrees for 20 minutes, and then reduce the temperature. Cook the bird for 20 minutes per pound, giving a 20-pound turkey six hours and 40 minutes to cook.