Preheat the oven to 175 degrees F. For the seasoned flour: In a bowl, mix the flour, Cajun spice and salt together well. For the chicken: Toss the chicken with the salt, pepper and 1/2 cup vegetable oil and place on parchment paper on a baking sheet. Slow cook in the oven until the internal temperature on an instant-read meat thermometer reaches 165 degrees F, about 2 hours (do not let the thermometer touch the bone). Then remove the chicken and cool. Heat a deep-fryer with the remaining 8 cups oil to 400 degrees F. Toss the cooled chicken with the seasoned flour and flash-fry, in batches if needed, in the fryer, cooking until the skin crisps, 3 to 4 minutes. Serve.