Prepare the ingredients: rinse the chicken and pat dry it with a paper towel; wash the lemons thoroughly and cut them into quite thick slices (about ½ cm); cut the whole garlic heads in half crosswise. Some of the cloves will separate, but don't worry about it.
Preheat the oven to 180℃. Line a deep baking tray with baking paper. You don't need to do it if you're using a glass dish, but you still can.
Place lemon slices on the bottom of the baking tray/form and arrange the garlic evenly between them.
Sprinkle the chicken tights with salt and pepper on all sides. Arrange them in a single layer, on lemons and garlic, skin side up. Add some thyme, if you want. Drizzle everything with olive oil.
Bake uncovered for about 30 minutes, then increase the temperature to 220℃ and bake for another 10-15 minutes until the skins are nicely browned and crispy. Every oven is different, so it may happen that especially large pieces would need to be left at a lower temperature for a little longer.
Wait a while before serving until the juices in the thighs settle down. A delicious lemon-garlic sauce will collect at the bottom of the dish, which is perfect for pouring over baked potatoes, or simply mopping it with a slice of good bread.