Slide 2 fingers under chicken skin and loosen enough to tuck 2 lemon slices, 4 garlic slices and 1 thyme sprig underneath the skin, directly over the breast meat of each chicken breast. Season chicken generously with salt and pepper. Place chicken in 9 by 13- inch glass baking dish. Pour 1 cup chicken broth, remaining sliced garlic and thyme sprigs in pan bottom.
Place in oven and roast until chicken is golden brown and cooked through, about 25 minutes. Remove chicken from pan and set aside. Pour pan juices into a small sauce pot. Add lemon juice. Reduce over medium high heat until sauce has thickened to almost a glaze. Taste and adjust seasonings with salt and pepper. Pour juices over chicken and serve immediately.