01 - Combine garlic, rosemary, thyme, Dijon mustard, olive oil, kosher salt, and black pepper in a small bowl. Mix thoroughly to form a consistent 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 plastic bag. Refrigerate for at least 1 hour, or up to overnight for intensified flavor penetration.
04 - Remove the lamb from the refrigerator 30 minutes before cooking. Preheat the oven to 425°F. Allowing the meat to reach room temperature promotes even cooking.
05 - Heat 1 tablespoon olive oil in a large ovenproof skillet over medium-high heat. Sear the rack for 2-3 minutes per side until a golden-brown crust forms.
06 - Transfer the skillet to the preheated oven. Roast for 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 the oven and tent loosely with aluminum foil. Let rest for 10 minutes to allow juices to redistribute throughout the meat.
08 - Slice the rack between the bones into individual chops. Sprinkle with flaky sea salt just before serving, if desired.