Place the flour in a shallow dish. Pat the chicken breasts dry with paper towels and season with salt and pepper. Working with 1 chicken breast at a time, dredge in the flour, shaking off the excess.
Heat 2 tbs of the oil in a 12 inch nonstick skillet over medium high heat until shimmering. Carefully lay the chicken breasts in the skillet and cook until well browned on the first side, 6-8 minutes.
Flip the chicken breasts over, reduce the heat to medium and continue to cook until the thickest part of the chicken is cooked through at the thickest part, about 6-8 minutes longer. Transfer the chicken breasts to a plate, tent loosely with foil, and let rest while cooking the vegetables and couscous.
Add 1 tbs more oil to the skillet and return to medium-high heat until shimmering. Add the onion, fennel and 1/2 tsp salt and cook until the onion is softened, 5-7 minutes. Stir in the couscous, garlic and a pinch cayenne and cook until fragrant, about 30 seconds. Stir in the 3/4 cup of the orange juice and broth, scraping up any browned bits. Bring to a simmer, cover, and let sit off the heat until the liquid is absorbed, about 5 minutes.
In the meantime, whisk the remaining 5 tablespoons oil, remaining 1/4 cup orange juice, 2 tbs of the cilantro and a pinch of the cayenne together in a small bowl; set aside.
Gently fold the remaining 2 tbs cilantro into the couscous with a fork and season with salt and pepper to taste. Drizzle the oil-orange juice mixture over the chicken and couscous before serving.