Couscous alla Trapanese

Name: Couscous alla Trapanese
Ingredients: 17 ounces boxed couscous; 2 bay leaves; 1 cinnamon stick; 10 garlic cloves, smashed (plus 2, unpeeled); 2 onions, chopped (plus 1, halved); 1/4 cup extra-virgin olive oil; 2 large stalks celery, chopped; 1 small bunch parsley, left whole, with a small amount reserved and chopped for garnish; 1/2 cup sliced almonds; 1 pound fresh tomatoes, peeled; 4 cups water; 1/2 pound large head-on shrimp, heads and bodies separated; 2 pounds mixed fish and shellfish, such as red snapper, sea bass, calamari, and mussels; Red pepper flakes, to taste; Salt and pepper, to taste; Lemon, for garnish, if desired