Preheat the oven to 450°F. Rinse the chicken, then dry it very well with paper towels, inside and out. The less it steams, the drier the heat, the better.
Salt and pepper the cavity, then truss the bird.
Next, salt the chicken- spread the salt evenly over the chicken, which will result in a crisp, salty, flavorful skin (about 1 tablespoon). Sprinkle about a teaspoon of pepper over as well.
In a bowl, toss the grape clusters and 2 chopped shallots in about a tablespoon of olive oil and light seasoning of salt and pepper.
Place the chicken in a sauté pan or roasting pan with the grapes and shallots surrounding it, then, place the pan in the hot oven. Leave it alone and roast it until it's done (165 degrees for the internal temperature of the bird), 50 to 60 minutes. Remove it from the oven and add the thyme, if using, to the pan. Baste the chicken and grapes with the juices and thyme and let it rest for 15 minutes on a cutting board.
Remove the twine and serve with grapes over polenta