How to Make It
Season chicken thighs with 1 1/4 teaspoons salt and pepper. In a heavy-bottomed skillet, heat oil over medium-high. Add chicken thighs, skin side down; cook, undisturbed, until nicely browned, 4 to 5 minutes. Flip and brown other side, 4 to 5 minutes more. Transfer to a plate, and set aside.
Pour off all but 2 tablespoons fat from pan; return to medium-low heat. Add fennel and leeks; cook, stirring often, until they begin to soften, 2 to 3 minutes. Add garlic, and cook 1 minute more. Stir in Pernod, scraping up any browned bits that have formed at the bottom of the pan. Cook until liquid is mostly absorbed, about 1 minute. Season with remaining 1/2 teaspoon salt.
Return chicken to pan along with any residual juices. Pour in enough of the stock to come halfway up chicken thighs; bring to a simmer. Partially cover, and cook until chicken is done and tender, 25 to 30 minutes.
To serve, spoon the braising liquid around the chicken with a showering of the tarragon and fennel fronds. Serve with lemon wedges and flaky salt, if desired.