Preheat the oven to 180ºC.
Heat the olive oil in a large ovenproof frying pan (Le Creuset or similar) over medium heat. Season the chicken pieces and add, skin side down, and sear until golden, about 5-7 minutes in total (depending on the size of your thighs), flipping half way. Transfer to a plate with a slotted spoon.
Pour all the oil out of the pan and then pour 2 tablespoons back in, keeping the rest to use later. Add the lemon wedges and garlic, and fry until the lemon wedges are charred on both sides. Transfer the lemon and garlic to the plate with the chicken.
Turn down the heat, add the onions, and let them sweat for a couple of minutes. Add a tiny bit more oil if needed. Then add the za'atar, oregano, fennel seeds and a pinch of sea salt to the pan, and stir to coat. Gently fry together over medium-low heat, stirring frequently, for 10 minutes or until the onions are soft, sweet and golden. Add more oil if they start to stick to the pan or colour too quickly. Pour in the alcohol and stir with a wooden spoon as it bubbles up to scrape up all the delicious bits stuck to the pan. Cook until the smell of alcohol subsides.
Arrange the chicken in the pan in a single layer, skin side up, then nestle the olives, lemon wedges and garlic in between. Pour the lemon juice over the top and add a little more salt and pepper. Roast for 30-35 minutes or until the chicken is cooke through. This dish is delicious served with rice or other grains, with the pan juices spooned over the top.