Take the turkey out of the fridge 1 hour before you plan on baking it.
Make the orange herb butter: combine soft butter with finely chopped herbs, grated orange zest, minces cloves garlic, and black pepper (I'm not adding any salt).
Spread the butter everywhere under the skin. Do not spread it on top of the skin - the herbs would burn in a hot oven. Brush the skin with olive oil.
Spread the turkey as flat as possible on the baking tray. For a large turkey, you can spread the legs more to the sides instead of tucking them close to the breasts.
Preheat the oven to 400°F (200°C).
When the oven is hot, place the baking sheet in the oven and bake the turkey until the skin is golden brown and the turkey is cooked through.
To check if the turkey is cooked through, measure the temperature of the meat with a thermometer. To measure the temperature correctly, insert the probe into the deepest part of the breast, being careful to not go so deep as to hit the bone. Confirm the temperature in both sides of the breast. It should reach 165°F (74°C) for the breast and between 170-175°F (77-80°C) for the thigh. I'm actually taking the meat out of the oven when the breast reaches 158°F (70-71°C) and it comes to a safe temperature while resting. You need to be careful to not overcook the breast meat (it will be dry) but you don't have to worry about the thighs - they actually are better when cooked longer.
I baked my 11 lbs (5kg) turkey for 1 hour and 20 minutes.
I baked a small 7 1/2 pound (3.4 kg) turkey for 45 minutes until the breast was at 145°F (63°C) then I turned on the fan+grill setting to brown the skin (you can also move the turkey one rack higher and turn on the burner) and baked the turkey until the breast has reached 158°F (70-71°C).
A large turkey - 18 lbs (8kg): I baked it for 1 hour and 20 minutes at 400°F (200°C) then I reduced the temperature to 325°F (160°C) (otherwise it would burn) and baked it for 40 more minutes (2 hours in total).
You can use an instant-read thermometer or a grill thermometer to measure the temperature. I especially recommend a grill thermometer - you insert the probe into the meat and it stays there for the whole baking time. The thin wire goes through the door of the oven and the thermometer stays outside. You can set your thermometer to the desired temperature and when your turkey reaches it, the timer will let you know that your turkey is ready. This way you don't have to check on the turkey and open the oven door which decreases the temperature of the oven.
Take the turkey out of the oven, transfer it to another baking sheet. Let rest for at least 15 minutes.
While the turkey is resting, make the gravy.