Porchetta-Style Roast Pork

Toast 2 Tbsp. fennel seeds in a dry small skillet over medium-high heat, tossing often, until fragrant and slightly darkened in color, about 4 minutes. Transfer fennel to spice mill or mortar and pestle and let cool. Add 1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt, 2 tsp. black peppercorns, and 1 tsp. crushed red pepper flakes; coarsely grind.

Place one 5½–6-lb. skinless, boneless pork shoulder (Boston butt), excess fat trimmed, in a 13x9" baking dish. Rub pork all over with 6 large garlic cloves, finely chopped, then coat with spice mixture, patting to adhere. Cover pork loosely with wax paper and chill 12 hours.

Preheat oven to 450°. Coat a large rimmed baking sheet with extra-virgin olive oil. Uncover pork and transfer, fat side up, to baking sheet; drizzle with 2 Tbsp. extra-virgin oil. Roast pork 30 minutes. Reduce oven temperature to 300° and continue to roast pork until very tender and an instant-read thermometer inserted into the thickest part registers 190°, 3–3½ hours longer. Carefully transfer pork to a cutting board and let rest 15–30 minutes; reserve baking sheet.