Prepare the couscous: Place the couscous in a bowl, drizzle with 2 tbsp olive oil, and fluff with a fork. Add 1 cup boiling water, cover, and let steam for 5 minutes. Fluff again and set aside. (Traditional method: steam couscous in a couscoussier for richer flavor.)
Cook the sauce: In a large pot, heat 1 tbsp olive oil. Add onion and garlic, sauté until soft. Stir in tomato paste, harissa, and spices, and cook for 2 minutes until fragrant.
Add the meat or fish: Add lamb or chicken pieces (if using fish, add later to avoid overcooking) and sear lightly in the sauce.
Simmer: Pour in stock, bring to a boil, then reduce to a simmer. Add carrots, zucchini, potato, and chickpeas. Cook for 30–40 minutes until meat is tender and vegetables are soft.
If using fish: Add fish pieces in the last 10 minutes of cooking.
Assemble: Spoon couscous into bowls or a large serving dish. Ladle sauce, meat/fish, and vegetables over the top.
Finish: Garnish with parsley or cilantro and serve with lemon wedges on the side.