01 - Combine garlic, rosemary, thyme, Dijon mustard, olive oil, salt, and black pepper in a small bowl. Mix thoroughly to form a cohesive paste.
02 - Pat the rack of lamb completely dry with paper towels. Rub the marinade paste evenly over all surfaces of the meat, ensuring full coverage.
03 - Place the coated lamb in a shallow dish or resealable bag. Refrigerate for at least 1 hour, or up to overnight for intensified flavor development.
04 - Remove lamb from refrigerator 30 minutes before cooking to reach room temperature. Preheat oven to 425°F.
05 - Heat 1 tablespoon olive oil in an ovenproof skillet over medium-high heat. Sear lamb for 2–3 minutes per side until deeply browned.
06 - Transfer skillet to preheated oven. Roast 15–20 minutes for medium-rare (125–130°F internal temperature), 20–25 minutes for medium, or 25–30 minutes for well-done.
07 - Remove from oven and tent loosely with aluminum foil. Let rest for 10 minutes to allow juices to redistribute throughout the meat.
08 - Slice between bones into individual chops. Sprinkle with flaky sea salt just before serving, if desired.