In a mortar and pestle, mash garlic, salt, oregano, cumin, and pepper together until you get a paste. Transfer to a bowl and combine the garlic mojo marinade with the oil and sour orange juice. Set aside.
Place the thawed turkey, breast-side down, on a cutting board or baking sheet. Run your hand along the center of the bird to find the backbone. Using a pair of very sharp kitchen shears, cut as close to the spine as possible, one side at a time.
Turn the turkey over, breast-side up, and using both hands, one on top of another, press down firmly on the breast until you hear a crack. Transfer the now flattened, spatchcocked turkey to a baking sheet with a wire rack.
Rub the marinade inside and under the skin. Pat the skin dry, brush it with oil and season with salt and pepper. Tuck the wing tips behind the turkey breast to prevent them from burning. Roast at 425° for 1.5 hours until browned and cooked through.