Heat oven to 400°F. Pat chicken dry and season with 1/2 teaspoon kosher salt and 1/2 teaspoon freshly ground black pepper. Crush the garlic cloves and remove peels. Mince one of the cloves and set aside.
Heat 2 Tablespoons olive oil in a 12-inch skillet over medium heat. When it begins to shimmer, add 5 crushed garlic cloves, 2 Tablespoons capers, 5 fillets oil packed anchovies, and 1/4 teaspoon red pepper flakes. Cook, stirring frequently until the garlic just begins to brown and the anchovies break down, about 3 minutes. Add the chicken thighs and cook until one side is browned, about 5 minutes. Remove any large pieces of garlic so they don't burn. Flip chicken thighs and transfer the skillet to the oven. Cook until the internal temperature of the largest part of the thighs measures 165°F, about 8-10 minutes.
Carefully remove the skillet from the oven and transfer the chicken to a plate. Place skillet over medium heat and add the reserved minced garlic and 1 Tablespoon lemon juice, scraping the skillet to remove any browned bits. Return the chicken to the skillet and sprinkle with 1 Tablespoon minced parsley. Serve immediately.
Notes
If you have extra oil from your oil packed anchovies, consider using some of it to replace the olive oil for extra flavor.