Pick the leaves from 1 fresh rosemary sprig and finely chop (about 1 ½ teaspoons). Finely chop 5 fresh sage leaves (about 1 tablespoon). Place both herbs in a small bowl, add 3 tablespoons of the kosher salt, and stir to combine.

Spatcock the turkey: Remove the neck and giblets, or save for another use. Pat the cavity and the outside of the turkey dry with paper towels and place breast-side down on a rimmed baking sheet. Using kitchen shears, cut along both sides of the backbone, then remove the backbone; discard or save the backbone for making turkey stock. Flip the turkey over. Firmly push down on the center part of the turkey breast until you hear the breast bone crack and the turkey lies flat.

Season both sides of the turkey evenly with the herb mixture both over and under the skin. Position breast-side up. Refrigerate uncovered for at least 4 hours or up to 1 day.

When ready to cook the turkey, arrange a rack in the lower third of the oven, remove any racks above it, and heat the oven to 450ºF. Meanwhile, place 1 stick unsalted butter in a small bowl and let sit at room temperature until softened.

Finely grate the zest of 1 medium lemon (about 1 teaspoon) into a food processor fitted with the blade attachment. Add ⅓ cup of the chili crisp and the remaining 1 tablespoon kosher salt. Pulse until combined, 2 to 3 (1-second) pulses. Transfer the mixture to the bowl of butter. Using a flexible spatula, smash and stir together until combined. (If you don’t have a food processor, finely chop the chili crisp, then just stir together with the butter, lemon zest, and salt.)

Cut the zested lemon plus 1 medium lemon crosswise into ½-inch-thick rounds. Peel and roughly chop 1 medium yellow onion into big chunks. Coarsely chop the white and light green parts of 3 medium leeks. Scatter the lemon, onion, and leeks across the bottom of a large rimmed baking sheet.

Rub the chili crisp butter all over the turkey (skin and bone sides). Place the turkey skin-side up on top of the vegetables.

Roast the turkey for 30 minutes. Reduce the oven temperature to 400ºF. Roast until an instant-read thermometer inserted into the center of the thickest part of the breast registers at least 150ºF and the center of the thickest part of the thigh not touching bone registers at least 165ºF, 40 to 45 minutes more.

Let the turkey rest for at least 10 minutes before carving. (You can use the roasted veggies and pan dripping under the bird for gravy.) Meanwhile, finely grate the zest of the remaining 3 medium lemons into a small bowl. Juice the zested lemons until you have 3 tablespoons and add to the bowl. Add the remaining ⅓ cup chili crisp and stir to combine.

Carve the turkey and transfer to a serving platter. Drizzle all over with the chili crisp mixture.