Place chicken thighs in a shallow dish. Drizzle with 1 Tbsp olive oil and rub ½ of the ras el hanout spice blend evenly over the thighs. Place in an airtight container and refrigerate for at least 8 hours, or overnight.
Preheat oven to 425°F. Place a cast-iron skillet over medium-high heat. Add remaining olive oil and the chicken thighs, skin-side down. Cook for 4-5 minutes or until the skin is golden brown. Turn the chicken over and cook another 2-3 minutes. Remove from the pan and set aside.