Preheat oven to 500°F. Set a wire rack on top of a rimmed baking sheet, lined with aluminum foil. Combine the salt, black pepper, and baking powder (and if you have other herbs you like to use) in a bowl and set aside. Also set aside 1 tbsp of oil.
Lay the chicken on a cutting board with breast side down. Use the poultry shears to cut along both sides of the spine to remove it completely from the chicken. Go ahead and cut the spine into pieces. These can be used to make gravy or stock later.
Set the chicken on the wire rack, with the spine side down. Spread open the chicken and press down on the breast so that most of the chicken is at the same height. Tuck in the wings, if you can.
Drizzle and rub the oil all over the chicken. Then sprinkle the seasoning evenly over the entire chicken. Try to rub the seasoning under the skin of the chicken with your fingers.
Roast the chicken for about 15 minutes. Reduce the oven temperature to 450°F. Take the chicken about of the oven. Cover the wings with foil to prevent it from burning and then roast again for about another 30 minutes. Cooking time may vary with size of the chicken. Use a meat thermometer to verify the chicken is cooked all the way through (150°F breasts, 175°F between the thighs and the body).
After removing the chicken from the oven, let it sit for 5 minutes before carving.