Heat the oil in a large pot or Dutch oven over medium heat. Add the onions, celery, carrots, garlic, salt, and pepper. Cook, stirring, until the veggies are tender, about 8 minutes.
Add the red pepper flakes, paprika, turmeric, and coriander. Cook, stirring, toasting the spices, about 2 minutes.
Add the chickpeas, broth, bay leaves, and lemon zest, and bring to a rapid simmer. Reduce the heat to a subtle simmer, about medium-low heat, and stir in the couscous and oregano. Cover and cook until the chickpeas and couscous is tender, about 10 minutes.
Add in the chicken, lemon juice, parsley, and dill, and stir to combine. Let simmer, uncovered, to warm the chicken and allow the flavor to meld in to the chicken, about 5 more minutes.
Discard the bay leaves. Taste and add salt, if desired. To serve, ladle into bowl and top with fresh dill.