Preheat the oven to 325 degrees F. Heat a wide braising pan or tagine over medium-high heat.
In a small bowl, combine the harissa, paprika, turmeric, cumin, ginger, cinnamon, coriander, allspice, cardamom, cayenne, orange zest and 2 tablespoons of canola oil. Stir to form a paste.
Season the chicken with salt and pepper; rub half of the spice mixture on both sides of the thighs.
Add the remaining 2 tablespoons canola oil to the pan. Sear the chicken skin-side down until golden brown, about 5 minutes. Flip and brown the other side. Remove to a plate.
Add the garlic, onion and remaining spice mixture to the same pan, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Reduce the heat to medium and cook until the onions are softened and lightly browned, about 5 minutes.
Return the chicken to the pan along with the tomatoes, chicken stock, olives, apricots, preserved lemon and sliced oranges and season with salt and pepper, being careful with the salt. Braise in the oven, partially covered, for about 1 hour and 15 minutes. Uncover and continue to braise until the chicken is tender, another 15 to 45 minutes. Serve from the pan over couscous, garnishing with sliced Meyer lemon and whole cilantro and mint leaves.