Preheat the oven to 190°C, fan 170°C, gas 5. Calculate the cooking time for the turkey using the information on the front of the package; it will be around 2 hours and 15 minutes.
Transfer it to a flameproof roasting tin after patting it dry with kitchen paper. Massage a thin coating of 25g butter into the skin all over. Drizzle with 2 tbsp oil; season well. Cover loosely with foil and place in the oven with a timer.
Meanwhile, combine the clementine zest and juice, honey, and half of the thyme in a saucepan. Cook for 10-15 minutes over medium-low heat, until the liquid has reduced to a light syrup. 25 g butter, melted Remove from the heat; discard the thyme.
Remove the foil from the bird after 45 minutes of cooking and baste with half of the honey glaze. Toss the onion and carrots into the tin's juices.
Return to the oven, uncovered, and baste with the remaining glaze every 15 minutes. If the glaze starts to catch, cover with foil.
For the last 5-10 minutes, increase the heat to gas 7, 220°C, fan 200°C. When the turkey is done, a kitchen thermometer should read 70°C in the center and juices should run clear when a skewer is withdrawn, with no pink meat visible.
Remove from the tray and let aside to rest for 30 minutes.
Preheat the oven to 350°F and place the tin with the vegetables on the stovetop. 10 minutes after adding the wine, let it bubble. Combine the stock, rosemary, and the majority of the thyme.
To make a paste, whisk together the flour and 4-5 tbsp water, then pour into the pan. Cook for 10-15 minutes, or until the sauce has thickened to your satisfaction. Strain into a warm gravy jug after adding any remaining liquids.
Meanwhile, saute the clementine halves cut-side down in a nonstick frying pan over high heat for 3-4 minutes, until golden and charred. To serve, arrange the vegetables around the turkey and sprinkle with thyme.