In a medium saucepan, combine water, kosher salt, and granulated sugar. Heat over medium heat, stirring until the salt and sugar are dissolved. Remove from heat.
Add crushed garlic cloves, bay leaves, and black peppercorns to the brine. Let it cool completely.
Place the chicken thighs in a large resealable bag or a container. Pour the cooled brine over the chicken, ensuring it is fully submerged. Seal the bag and refrigerate for at least 4 hours, or preferably overnight.
When ready to cook, remove chicken from the brine and pat dry thoroughly with paper towels. Discard the brine.
Preheat your oven to 400°F (200°C).
Place the dried chicken thighs on a baking sheet, skin-side up. You can season with additional pepper if desired, but avoid salt as the chicken will be well-seasoned from the brine.
Roast for 40-45 minutes, or until the internal temperature reaches 165°F (74°C) and the skin is golden brown and crispy.
Let the chicken rest for a few minutes before serving.
Notes
For an even crispier skin, you can broil the chicken for the last 2-3 minutes of cooking, watching carefully to prevent burning.