Make the herb paste. Combine the garlic and salt in a mortar and pound until you have a smooth paste. (If you don’t have a mortar, make the paste using a chef's knife. Transfer to a small bowl and stir in 2 tablespoons olive oil, herbs, pepper, and celery seeds.
Season and tie the turkey breast. Smear the turkey breast all over with the herb paste, using your fingers to slide some of the paste under the skin, being careful not to loosen the skin completely. Using your hands, arrange the turkey breast in a neat shape, tucking the edges under so the breast sits plumply on the cutting board. Now tie the breast, using 2 to 3 loops of kitchen string to secure it in a cylindrical shape and looping a longer string from end to end to keep the roast compact. Place the roast on a wire rack on a baking sheet or tray and refrigerate, preferably uncovered, for 6 to 24 hours. Let the roast sit at room temperature for about an hour before roasting.
Heat the oven. Position a rack near the center of the oven and heat to 300 degrees (275 degrees convection).
Sear the turkey. Heat a large skillet (11 to 12 inches) over medium-high heat. Add the remaining tablespoon oil and heat until the oil shimmers. Sear the turkey skin side down, maneuvering it and turning it from side to side with tongs so the skin side sears evenly, about 6 minutes. Turn the turkey skin side up and brown lightly on the bottom, another 2 to 3 minutes. Transfer the turkey, skin side up, to a shallow roasting pan or baking dish not much larger than it is (about 8 by 12 inches).
Roast. Slide the turkey into the oven and roast until the juices run mostly clear with a trace of pink and an instant-read thermometer inserted in the thickest part registers about 165 degrees, 1 1/2 to 1 3/4 hours. Let the turkey rest for 20 minutes.
Carve and serve. Remove the strings and carve the turkey across the grain into 1/4- to 1/2-inch-thick slices. There will be few, if any, pan drippings (because of the preseasoning and slow cooking), but if there are a few, drizzle these over the meat.
Recipe courtesy of All About Roasting by Molly Stevens/W.W. Norton & Company, 2011.