Classic Roasted Chicken with Pan Gravy

Heat the oven to 425°F.  While the oven is heating, remove the package of the giblets and neck from the chicken cavity.  Rinse the chicken with cold water and pat dry with a paper towel.  Season the chicken inside and out as desired.  Place the onion, garlic and thyme sprigs into the chicken cavity.  Fold the loose skin over the cavity.  Tie the ends of the drumsticks together.
Place the chicken, breast-side up, on a rack in a shallow roasting pan.  Brush the chicken with the oil.  Insert a meat thermometer into the thickest part of the meat, not touching the bone.
Reserve 1 1/2 cups broth for basting.  Roast the chicken for 1 1/2 hours or until the internal temperature reaches 165°F. the skin is a deep golden brown and the juices run clear. Baste the chicken with the reserved broth every 30 minutes of roasting time.  Discard any remaining broth used for basting.
Remove chicken to a cutting board, cover and keep warm.  Let chicken stand for 20 minutes.   Strain the drippings from the pan into a bowl.  Spoon off any fat.  Whisk 1/2 cup broth and the flour in a small bowl until smooth. 
Return the remaining 2 cups broth and the strained drippings (plus any juices from the chicken on the cutting board) to the roasting pan.  Heat on the stove over medium-high heat to a boil.  Cook for 2 minutes, stirring to scrape up any browned bits from the bottom of the pan.  Gradually stir in the flour mixture.  Cook and stir for 4 minutes or until the mixture is thickened.  Season to taste.  Serve the gravy with the roast chicken.