Cut up the veggies into chunks and season them with salt and pepper. Assemble them throughout the baking pan, leaving space in the center to nestle the turkey.
Whisk the mayonnaise, salt, pepper, and pressed garlic together.
Using poultry shears, remove the backbone from the turkey.
Carefully, pull the turkey skin away from the flesh in several different sections across the bird.
Spread the marinade underneath the skin generously.
Roast the turkey at 400°F for 60 minutes. Then, turn the heat down to 350°F and bake the turkey for another 2 hours. Remove the turkey from the oven and cover it with foil or a lid. Allow it to rest for 30 minutes before carving into it!