Preheat oven to 425°F | 220°C for standard ovens, or 390°F | 200°C for fan forced. Lower oven shelf to the lowest part of your oven.
• Defrost the Turkey (24 hours per 3-4 lbs/1.5-2 kg). Keep it in its packaging in a deep pan to catch drippings. Remove the neck and giblets, rinse inside and out, then pat the turkey dry with paper towels.
  
Pro Tip: For faster thawing, place the turkey in a sealed, leak-proof bag. Submerge it in cold water, allowing 30 minutes per pound (500g). Change the water every 30 minutes to keep it cold. Let the turkey rest at room temperature for 30-60 minutes before cooking.
• Combine the Herb Butter ingredients in a bowl and mix well. Reserve half of the herb butter in the refrigerator for later.
  
• Arrange the 4 halves of garlic cut-side down on the bottom of the pan with 4 sprigs each of thyme and rosemary, half of the olive oil, and 1 slice of lemon. Stuff with the remaining garlic halves, a lemon slice, a squeeze of lemon from the remaining slice, herbs and a drizzle of olive oil. 
  
A roasting pan with a wire rack is always best. If you are using a standard baking tray, use the halved garlic heads as a makeshift rack. Just make sure to line the tray with foil or parchment paper if it isn't nonstick, so the skin of the turkey doesn't stick to the bottom!

Initial Sear (First 30–45 mins)

• Melt the butter and rub all over the turkey, including under the skin. Season generously all over with salt and pepper. Place turkey on top of the garlic and herbs in the pan BREAST-SIDE DOWN. Drizzle with the remaining oil.
  
Roast uncovered for 30 minutes for a small turkey under 13 pounds (6 1/2 kg), or 45 minutes for a larger turkey over 14 pounds (7 kg plus).
• Turn turkey over (breast-side up) with a pair of tongs, a clean tea towel or oven mitts (heat-proof gloves), and baste with pan juices.
  
• Spread half of the reserved herb butter over the top of your turkey with a spoon or brush (be careful, the turkey will be hot and the butter will melt nicely over the skin). Pour any remaining juices over your turkey.
  

Basting & Finishing

Reduce heat to 325°F |165°C (for standard ovens), or 300°F | 150°C (fan-forced). Roast, uncovered, for an hour.
• Slather turkey generously with remaining butter and roast for 30 minutes. Baste again, then continue roasting for a further 30 minutes or so, depending on the size of your bird. Tent loosely with foil if starting to brown too fast.
  
For an extra-large turkey, you may need an additional half hour to an hour.
For extra crispy skin, broil (or grill) in the last 5-10 minutes, keeping an eye on it so it doesn't burn, until the skin is crispy and golden-brown all over.
• Tent the turkey with foil and allow it to rest for 20-30 minutes before carving and serving.
  
Remove 2 1/2 cups of the liquid from the pan juices (top up with stock if you need to), strain, and reserve for your gravy. 

How To Make the Gravy

• Melt the butter in a pan over low heat, mix very well, and add the flour. Once the ingredients are mixed, add the pan juices, and it's very important not to stop mixing while adding them.
  
Season to taste with salt, pepper, Worcestershire sauce, or herbs.