Heat oven to 450° F. Gently loosen the chicken skin from the breast meat and place a third of the thyme and tarragon under the skin. Place another third of the herbs, plus the lemon and a handful of garlic cloves, inside the chicken cavity, and tie the legs together with cooking twine.
Place the chicken in a small roasting pan and surround with the remaining herbs, garlic, and olives. Sprinkle the chicken with the salt and pepper and drizzle with the olive oil.
Roast the chicken for about 1 1/2 hours, or until the thigh juices run clear when pricked with a fork or an instant-read thermometer inserted in the thigh reads 170° to 175° F. Transfer the chicken to a cutting board, cover loosely with foil, and let rest 15 minutes. Skim the fat from the pan juices.
Place the chicken on a platter with the roasted olives and garlic and spoon the pan juices over it. Serve with the baguette slices, which will sop up the juices and can be spread with the roasted garlic.