In a small food processor, blend together the garlic, sage, rosemary, thyme, salt and olive oil. Rub the paste over the chicken thighs, getting the mixture under the skin. Place in a container with a lid, or in a bowl and cover, and refrigerate from 6 to 24 hours.
Preheat the oven to 425°F. While the oven preheats, bring the chicken to room temperature. Place the lemon slices in a 13x9 inch baking pan. Place the marinated chicken on top of the lemon. Sprinkle with kosher salt and pepper. Bake for 45 to 55 minutes, until the juices run clear when the chicken is pierced with a sharp knife (an internal temperature of 165°F), and the skin is golden brown and crispy.
Line a serving platter with arugula, if desired. Transfer the chicken to a the serving platter, with the lemon slices interspersed.
Place the baking dish over a burner set to medium high heat and simmer the juices in the pan, scraping to loosen any caramelized bits from the bottom of the pan. Drizzle the sauce around the chicken to keep the skin crispy, but (and hopefully you are entertaining people you really like) pass chunks of bread around so people can sop up some of the delicious sauce on the platter.
Notes
Chicken thighs roast up beautifully with all kinds of herbs, and if you have easy access to multiple fresh herbs, you can rustle up some very sophisticated and nicely flavored thighs by using a blend. I used sage, thyme, and rosemary, but if you wanted to use just one herb, you would have delicious chicken thighs. This is a great way to use up leftover herbs, or to take advantage of that lovely herb garden you have been working on.