Preheat the oven to 175°C (350°F) or 160°C fan.
Pat the chicken dry and season generously with salt and pepper.
Heat olive oil in a large Dutch oven or casserole dish.
Cook the bacon lardons until crisp, then remove and set aside.
Sear the chicken on all sides until golden brown.
Add onion, carrots, celery, and garlic to the pot and cook until slightly softened.
Sprinkle in the flour and stir for 1–2 minutes.
Pour in the white wine and scrape up any browned bits from the bottom of the pot.
Add chicken stock, thyme, and bay leaf. Stir well.
Return the chicken and bacon to the pot.
Cover with a lid and roast for 1 hour 15 minutes to 1 hour 30 minutes.
Check that the internal temperature reaches 74°C (165°F).
Transfer the chicken to a board and rest for 15–20 minutes.
Simmer the gravy if needed until thickened, then stir in parsley.
Carve the chicken and serve with vegetables and gravy.