Place the chopped chicken in a bowl with the pepper, salt, 1 tsp of the cumin, cinnamon, coriander, paprika, lemon juice, 3 of the crushed garlic cloves, sumac and all but 1 tsp of the olive oil. Mix, cover and refrigerate for 1-2 hours (up to overnight).
When ready to cook, heat a large griddle or frying pan on a high heat and add in the chicken pieces to the dry pan. Cook for 6-8 minutes, turning occasionally, until cooked through and no longer pink in the middle.
Whilst the chicken is cooking, make the couscous. Add the couscous to a large jug with a pinch of salt and pepper, the lemon zest, the remaining crushed clove of garlic, a pinch of the chilli flakes and the boiling water. Stir, cover and leave to sit for 5 minutes, then fluff with a fork.
Next add the remaining 1 tsp of olive oil to a small frying pan. Add the chickpeas, the remaining 1 tsp of cumin, the smoked paprika and a pinch of salt and pepper. Cook over a high heat, stirring regularly for 5 minutes, until the chickpeas are warmed through and slightly golden. Turn off the heat.
Now it’s time to assemble. Divide the couscous between four bowls. Add the salad leaves, chickpeas, and flatbread slices. Place the cooked chicken on top, then spoon on the hummus. Sprinkle on the sliced spring onions and arrange the radish slices and tomatoes on top. Sprinkle with a good pinch of chilli flakes and the chopped parsley, then serve.