Preheat oven to 390℉(200°C). Rinse chicken cavity under cold water. Pat dry inside and out with a paper towel.

Combine the butter and thyme leaves in a small bowl. Season with salt and pepper.

Lift the skin under the breast. Spoon the butter mixture under the skin. Place four slices of the lemon under the skin.

Place remaining lemon into the chicken cavity with six sprigs of lemon thyme. Tie the legs together with kitchen string.

Place the chicken in a large roasting pan. Place the onions, potatoes, and fennel in a large bowl.

Drizzle with half the oil. Gently toss to combine. Arrange around the chicken. Drizzle remaining oil over the chicken and season well with salt and pepper.

Roast the chicken in the preheated oven, occasionally basting in pan juices, for 1 hour 15 minutes or until the juices run clear when a skewer is inserted into the thigh.

Remove from oven and set aside for 10 minutes to rest. Serve with steamed beans and peas to serve.