I really love the way the lemon adds such a zest to this dish; it plays perfectly with the garlic and thyme. For a quick, simple go-to dinner, this one is certainly in my top 5 list.
In a large bowl, toss together the potatoes, carrots, garlic cloves, onions and celery in 1 tablespoon of the olive oil, generously adding salt and pepper.
Drizzle the remaining tablespoon of olive oil over the chicken pieces, add some salt and pepper, and rub it in well.
Lay the fresh thyme sprigs over the chicken, then arrange the remaining lemon slices around, and bake for about 45 - 60 minutes, or until the chicken is cooked through.
Remove the chicken to a platter, cover with a foil tent. Turn your broiler on and return the vegetables to the the oven, close to the top, and allow to roast and brown for about 5 - 10 minutes, keeping a close eye on them so they don't burn.
Serve the chicken over the vegetables, and spoon some of the collected sauce in the bottom of the pan over the top.