Preheat the oven to 420 °F, (convection roast if you have it).
In a 14-15 inch metal or cast iron roasting pan, toss together the garlic cloves, ⅛ teaspoon kosher salt, green pitted olives, lemon slices, shallots, fennel and 1 tablespoon of extra virgin olive oil until evenly coated. Spread it all out in an even layer in the roasting dish and set aside.
In a small bowl, combine zaatar, ground cumin, garlic powder, ground sumac, ⅛ kosher salt, fresh lemon juice, honey lemon zest, and 3 tablespoons of extra virgin olive oil. Mix well until combined.
Trim chicken of excess fat. Using chicken sheers or a very sharp knife, cut a 1½-1¾ inch long slit through the skin on top of each chicken thigh (this is actually really important).
Rub the marinade under the skin and all over each chicken thigh. Allow the chicken to marinade for 30 minutes or up to overnight in the fridge.
Preheat a large skillet with 2½ tablespoons of extra virgin olive oil on medium high. Carefully place each chicken thigh, skin side down into the skillet and sear for 1-2 minutes, until the skin is medium golden brown (You will need to work in batches, do not overcrowd the pan). Turn the chicken over and let it cook for about 20-30 seconds. Remove chicken from the pan and nestle on top of vegetables in the roasting dish.
Lightly drizzle honey over the chickens and sprinkle a little extra dusting of zaatar and ground sumac. If you have fresh zaatar sprigs, stick them under the chicken skins and on top of the chicken.
Put the roasting dish in the oven and cook for 50 minutes-1 hour until the chicken thighs read on a 190 °F thermometer. . Be sure occasionally baste the chicken. If the roasting pan runs a bit dry, you can add 1/4 cup warm water to the pan or a dry white wine.
Remover the chicken from the roasting dish onto a platter and cover well with foil to let it rest.
Preheat the broiler on medium. Put the roasting dish under the broiler (with everything but the chicken) for 1 minute or a touch more, until the fennel gets color and a bit of a sear.
Remove the roasting dish from the broiler, remove the foil from the chicken and spoon the contents of the roasting dish over the chicken.
Notes
This chicken keeps well covered in foil and left in a 200 degrees oven until ready to serve.