Season the chicken all over with 2 tsp. salt and 2 tsp. pepper. Heat the oil in an 8-quart Dutch oven over medium-high heat. Working in batches so as not to crowd the pan, brown the chicken well all over, about 3 minutes per side, transferring each batch to a plate or bowl—it'll take about 4 batches and 24 minutes total to brown all the chicken. The bottom of the pan will be brown, but that's OK.
Reduce the heat to medium, add the onions and garlic and cook, stirring occasionally until the onions are softened and golden brown, 5 to 6 minutes. Add the turmeric, cumin, coriander, chiles, cinnamon sticks, and bay leaves and cook, stirring constantly, until fragrant, about 1 minute more. Add the chicken broth, lemon zest, and 1/2 cup of the lemon juice. Cover and simmer over medium-low heat for 30 minutes.
Return the chicken and any accumulated juices to the pot. Carefully stir in the chickpeas and olives. Increase the heat to medium high and simmer uncovered, stirring occasionally, until the sauce has thickened somewhat and the chicken is cooked through, 6 to 8 minutes more. Stir in 1 Tbs. of the remaining lemon juice and season to taste with salt and pepper. Serve over the Saffron Couscous, sprinkled with the cilantro or mint.
This stew can be prepared and refrigerated up to 3 days ahead or frozen up to 1 month in advance. Reheat gently over medium-low heat, adding 1/2 cup water if the stew seems too thick.