Heat the oven to 220 C / 425 F.
Pat the chicken thighs completely dry with paper towels. Season both sides with salt, pepper, and oregano.
Heat olive oil in a 30 cm / 12-inch oven-safe skillet over medium-high heat. Sear 4 thighs skin-side down at a time, about 5 to 6 minutes, until the skin is deep golden and crisp. Flip and sear 2 minutes more, then set aside. Repeat with the remaining 4 thighs.
Pour off all but 1 tablespoon of fat from the skillet. Add the garlic and cook for 30 seconds, until fragrant, stirring so it doesn't burn.
Return all the chicken thighs to the skillet, skin-side up. Tuck lemon slices and thyme sprigs between the pieces, then scatter the olives around the chicken.
Pour the chicken broth and lemon juice into the skillet around the chicken, not over the crisp skin.
Transfer the skillet to the oven and roast for 25 to 30 minutes, until an instant-read thermometer inserted into the thickest part of a thigh, away from the bone, reads 165 F / 74 C.
Remove the skillet from the oven and let the chicken rest for 5 minutes in the pan juices.
Spoon the pan juices, olives, and roasted lemon slices over the chicken. Scatter parsley on top and serve.