Preheat the oven to 180°C and roast the chillies for 10 minutes.
Roughly chop the cooled chillies and simmer them with garlic, salt, oregano, paprika, oil, and vinegar for 3 minutes.
Blend the cooled mixture into a smooth purée and store in a lidded container.
Coat the spatchcocked chicken in half of the sauce and marinate in the refrigerator for at least one hour.
Preheat the oven to 200°C and heat a large griddle pan or barbecue.
Season the chicken and sear it on the griddle for 3 minutes per side.
Roast the chicken in the oven for 30 minutes until fully cooked.
Serve the chicken with chips and salad.