For the turkey: The day before serving, pat the turkey dry using paper towels. Remove the neck. Place the turkey on a large, clean cloth and rub both the inside and outside generously with salt. Place the turkey and the neck in a container that fits comfortably and refrigerate, uncovered, overnight to allow the skin to dry out.
Remove the turkey at least 2 hours prior to roasting to take the chill off it. Position the oven rack on the lowest rung and preheat the oven to 425 degrees F.
Place the oranges, 1 onion, cinnamon stick and thyme in the body cavity of the turkey. Fold the wings and tuck the tips underneath the bird.
For the butter sauce: Melt the butter in a small saucepan over medium heat. Add the maple syrup, mezcal and cloves. Bring to a gentle boil, then reduce to a simmer and cook, stirring occasionally, until fully incorporated, about 5 minutes. Remove from the heat and allow to cool slightly.
Place the remaining quartered onions in the bottom of a roasting pan to act as a rack. Add the turkey neck, along with the sage. Drizzle the onions and neck with olive oil and season with salt and pepper. Set the turkey on top of the onions. Soak a double layer of cheesecloth big enough to cover the bird in the butter sauce, then drape it over the breast and legs of the turkey. Pour any remaining butter sauce over the turkey. Add the stock to the bottom of the pan.
Roast for 45 minutes. Reduce the oven temperature to 375 degrees F and continue roasting until the skin is golden brown and the turkey juices run clear when an instant-read thermometer inserted into the thickest part of the thigh and breast registers 160 degrees F, another 10 to 15 minutes per pound (at least 1 hour and 40 minutes and up to 3 hours).
Allow the turkey to rest at least 30 minutes before removing the cheesecloth and carving.