Preheat the oven to 200°C conventional / 180°C fan / Gas Mark 6.
Place the chicken thighs in a bowl. Add the smoked paprika, dried mixed herbs, garlic granules and a little salt and black pepper. Turn the chicken until evenly coated.
Heat the vegetable oil in a large ovenproof casserole dish over a medium-high heat.
Add the chicken thighs and cook for approximately 2–3 minutes on each side, until lightly browned. They do not need to be cooked through at this stage. Transfer them to a plate.
Add the onion, red pepper and carrot to the same dish. Cook for 4–5 minutes, stirring occasionally, until beginning to soften.
Add the crushed garlic and cook for a further minute.
Stir in the uncooked rice, ensuring it is evenly coated in the vegetables and cooking juices.
Mix the tomato purée into the hot gluten-free chicken stock, then carefully pour it into the dish. Stir well and bring the liquid to a gentle simmer.
Place the browned chicken thighs on top of the rice. Cover the dish tightly with a lid or foil.
Transfer to the oven and bake for 35 minutes.
Carefully remove the dish from the oven. Lift the lid or foil away from you to avoid the steam.
Stir the frozen peas through the rice, then return the chicken to the top. Cover and bake for a further 10 minutes.
Check that the rice is tender, the liquid has been absorbed and the chicken is thoroughly cooked. The thickest part of the chicken should reach at least 75°C.
Leave the bake to rest, covered, for 5 minutes before fluffing the rice gently with a fork and serving.