Preheat oven to 450 degrees. Rinse and thoroughly dry the spatchcocked chicken with paper towels. Grind the lemon zest and dry spices in food processor.
Place the chicken in a pan and coat with oil, followed by the spice blend. Put the lemon slices under the bird. Roast uncovered for 45-50 minutes. Temperate should read 165 degrees when done.
To make the pan sauce, drain the juices from around the chicken into a cup using a baster. Skim as much fat off as possible; set aside.
In a small pot or pan add the butter and garlic over medium-low heat until fragrant. Next, whisk in the flour to make a roux and cook for about one minute. Whisk in the water and the pan liquid. Let it simmer for 1-2 minutes and turn off the heat. Serve hot with the chicken.