1 1/2 pounds chicken thighs, skin-on, bone-in, trimmed of excess fat
1 tablespoon whole grain mustard
1 tablespoon lemon zest (1 teaspoon for rub and 2 teaspoons for sauce)
1 1/2 teaspoons dried oregano
1/2 teaspoon dried thyme
1/4 teaspoon kosher salt
2 tablespoons olive oil (1 tablespoon for rub, 1 tablespoon for cooking)
1/4 cup lemon juice (about 1 lemon)
1 1/4 cups low-sodium chicken stock
2 garlic cloves, smashed
1 tablespoon unsalted butter
1 tablespoon all-purpose flour