Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Once the oil shimmers, add the frozen chicken thighs, skin side down. Sear for 5 minutes until the skin is golden brown and releases easily.

Flip the chicken thighs and season with salt and black pepper. Continue cooking for another 5 minutes. The skin should be crisp, and the chicken should begin to thaw and cook through.

Reduce the heat to medium and add the remaining olive oil. Add minced garlic and dried thyme, stirring until fragrant, about 30 seconds. The garlic should turn a light golden color.

Add the chicken broth to the pan, ensuring to scrape up any browned bits stuck to the bottom. This deglazing process enhances the sauce's complexity and prevents any potential sticking or burning. Allow the broth to simmer gently, releasing a savory aroma, while stirring occasionally for about 5 minutes.

Cover the skillet with a lid and reduce the heat to low. Simmer for 15 minutes, allowing the chicken to cook through. The steam will help maintain moisture and ensure even cooking.

Check the internal temperature of the chicken with an instant-read thermometer. It should reach 165 F (74 C) for safe consumption. If not, continue cooking covered, checking every 5 minutes.

Once the chicken is cooked through, remove the lid and turn the heat to medium-high. Add lemon slices to the pan, cooking for 2 minutes. This will allow the lemon to soften and release its juices, creating a fragrant aroma and enhancing the sauce's flavor.

Transfer the chicken thighs from the skillet to a plate, allowing them to rest for about 5 minutes. This resting time helps the juices redistribute throughout the meat, resulting in a more tender texture. Avoid cutting into the chicken immediately, as this can cause the juices to escape, leading to drier meat.

Continue simmering the sauce over medium heat for an additional 3 minutes, allowing it to reduce slightly. As it thickens, the aroma will become more pronounced, enhancing the overall depth. Stir occasionally to prevent sticking and ensure even reduction, resulting in a sauce that complements the chicken perfectly.

Serve the chicken thighs with the sauce spooned over the top. Garnish with chopped parsley for a fresh finish. The contrast of the rich sauce with the fresh herbs completes the dish.