With the rack in the middle position, preheat the oven to 180°C (350°F).
Using the tip of a paring knife, cut 16 small slits all over the roast and insert a quarter garlic clove in each slit. Season the roast with salt and pepper.
In a bowl, combine the chopped garlic, 15 ml (1 tablespoon) oil, lemon zest and thyme. Set aside.
In an ovenproof skillet over medium-high heat, brown the meat on all sides in 30 ml (2 tablespoons) oil. Remove the roast from the skillet and rub with the garlic–lemon mixture. Place the carrots in the skillet and set the roast on top. Transfer to the oven and roast uncovered until a thermometer inserted in the centre reads 63°C (145°F), about 40 minutes.
Remove from the oven and tent with aluminum foil. Let rest for around 10 minutes before cutting into thin slices.