Drain any liquid that may have accumulated in the cavity of the turkey and thoroughly pat the bird dry with paper towels inside and out.
Season the turkey liberally with salt and pepper both inside and out, then place the rosemary, thyme, sage, onion, celery and carrot inside the cavity.
Tuck the wings behind and under the back of the bird and tie the drumstick ends together with kitchen twine.
Place the turkey breast side up on the roasting rack and set aside for 1 hour to come to room temperature.
Make the herb coating:
Combine the mayonnaise, sage, thyme, rosemary and garlic powder.
Cover and set aside to allow the flavor to develop.
Roast the turkey:
Position a rack in the lower portion of the oven and preheat it to 425°F.
Using a spatula, coat the turkey completely with half of the mayonnaise-herb mixture, being sure to get into the crevices where the legs and wings meet the body. Pour 2-1/2 cups of the chicken broth into the bottom of the roasting pan.
Roast for 30 minutes at 425°F, then rotate the roasting pan in the oven to ensure even browning and reduce the temperature to 325°F.
Continue roasting for 45 minutes, then remove the turkey from the oven, coat with the remaining half of the mayonnaise and herb mixture and add another 1/2 to 1 cup of chicken broth to the roasting pan. Return the turkey to the oven, rotating the pan once again.
Roasting time for a whole, unstuffed turkey is approximately 13 minutes per pound, so at this point, depending on size, you can expect to cook the bird for an additional 1 to 1-3/4 hours. This time can vary though, so you'll want check the temperature 30 minutes after returning the turkey to the oven to avoid overcooking.
To properly check the temperature, insert an instant-read thermometer into the meatiest part of the thigh. Be careful not to touch bone with the thermometer or you won't get an accurate reading.
The turkey should be done when the internal temperature of the thigh registers 165°F.
Remove the turkey from the oven, reserve the pan juices for gravy (see below), and let it rest for 20 to 30 minutes before carving.
Tips for Making This Recipe
How To Make Pan Gravy:
While the turkey is resting, skim any excess fat from the pan juices and transfer to a 4 cup measure.
Add enough extra chicken broth to equal 3 cups of liquid total.
Pour the broth into a saucepan and bring to a simmer over medium heat.
In a small bowl, whisk together the 1/4 cup cornstarch with 1/3 cup water.
Add to the simmering broth and continue whisking just until thickened and smooth.
Season to taste with salt and freshly ground black pepper.