Pat the whole chicken dry with a paper towel.
Heat olive oil in a large, heavy based pot then place the whole chicken into the pot and brown the skin well on all sides, turning it over as needed until the skin is a good golden brown color. Remove the chicken from the pot and set aside.
Place the sliced onions into the pot and fry until golden brown, then add the carrots and garlic and fry for 5 minutes, stirring occasionally.
Return the chicken to the pot, breast side up on top of the vegetables.
Squeeze the lemon juice over the chicken and sprinkle with rosemary. Add the stock together with the water and arrange the baby potatoes around the edge of the pot. Sprinkle a pinch of salt and pepper, to taste, on top of the chicken.
Cover the pot tightly with a lid or thick aluminum foil and allow to cook for 1 1/2 hours or until the chicken is cooked through and the vegetables are tender. You can turn the chicken over half-way through cooking. The internal temp you are looking for when measured with a meat thermometer is 82 C / 180 F when checked at the thickest part of the thigh without touching the bone.
Remove the chicken from the pot once cooked and allow to rest for a few minutes before carving. Serve with green beans and rice or potatoes.