In a medium bowl, add the butter, shallots, sage, rosemary, thyme, garlic, salt, and pepper. Mix well until smooth. Set aside.
Preheat the oven to 450°F and line a baking sheet with aluminum foil or use a large baking stone.
Remove the giblets and neck from the turkey and discard.
On a work surface, place the turkey breast side down. The backbone should be facing up. Use a pair of poultry shears to cut along each side of the backbone to completely remove it. (Discard the backbone or use it for broth or gravy.)
Flip over the turkey so it is now breast side up. Turn the legs in, towards the breast. Using your hands, press down to flatten the turkey. You may have to press down a few times.
Tuck the wing tips behind the breast and cut off any excess skin or fat around the neck area. Place the turkey onto the lined baking sheet and pat dry with paper towels. (It's important to get the skin dry so that the butter will adhere.)
Gently loosen and lift the skin from the turkey breast without totally detaching the skin. (You can use rubber gloves here.) Rub 3 tablespoons of the herb butter under the skin.
Rub the remaining herb butter on the top of the turkey.
Roast the turkey for 60-90 minutes, or until the internal temperature reaches 165°F.
Remove from the oven, tent with foil, and let it rest for 15 minutes before cutting and serving.