In a large pot or container (at least 6 quarts) add the salt, sugar, garlic, and peppercorns. Pour a gallon of warm water over the ingredients and stir until the salt and sugar are dissolved.
Put the pot or container in your fridge until the brine mixture cools.
In the meantime, get your chicken ready. Remove the giblets and any excess fat. When the brine mixture has cooled down, put the chicken in the pot or container with the brine. Put the container in the fridge for at least 8 hours. Flip it over about half way through. You can leave it for as long as 24 hours, but it’s not necessary.
Preheat oven to 425 F.
Put the chicken in the oven. Turn on the timer for 15-20 minutes. Lower the temperature to 350 F (although I like to put it somewhere between 350 and 375) and continue cooking your chicken according to the weight (see notes). If you have a meat thermometer, check it before you take it out to make sure it is 165 F for safety. Let it rest for about 10 minutes so the juices can distribute evenly throughout the bird.
Cook the chicken 20 minutes per pound, after the initial 20 minutes at 425° F. Total cooking time will be around 2 hours or more.
Adapted from Allrecipes