Make sure your turkey has been completely defrosted and padded dried.
Roughly chop the Mirepoix (carrots, onions and celery). No peeling needed, just washed.
Add Mirepoix to the bottom of your roasting pan.
In a food processor blend rosemary, sage, thyme, lemon zest, lemon juice, and garlic with a splash of olive oil, a pinch of salt, and black pepper.
In a mixing bowl add the softened butter, the herbs blend, kosher salt, and black pepper, and mix well.
Remove the giblets from the turkey and place them at the bottom of the roasting pan.
With your fingers get under the turkey skin very gently, without breaking the skin. You may use a small spatula, do not use any sharp objects.
Stuff seasoned butter under the skin. The rest of the butter mixture rub all around the bird.
Season the cavity with a pinch of salt and black pepper.
Inside the turkey cavity, add a couple of pieces of onions, carrots, and celery from the Mirepoix.
Roast at 325° until the internal temperature reaches 165°. That's about 15 minutes per pound. Mine took about 3 hours.
Let the turkey rest between 20 to 30 minutes before carving.
In a pot over medium heat, add 2 tablespoon of butter.
Once the butter melts, add the flour and let it cook off, for about a minute or two.
Remove all vegetables and liquid from the bottom of the roasting pan and add to the pot.