Preheat the oven to 425 degrees F. Place a large skillet or roasting pan in the oven to preheat while you prepare the chicken.
Begin by preparing a lemon butter. Place 4 tablespoons of the butter in a mixing bowl and add about 1 teaspoon of zest from the lemons. Season with salt and pepper and mix well.
Flatten the chicken by cutting out the backbone and flattening the breast by firmly pressing with the heel of your hand. Sprinkle both sides of the chicken with salt and pepper. Using your fingers, loosely separate the skin from the breast and thighs. Smear the lemon butter evenly in the cavity between the skin and meat, ensuring it is worked evenly over the bird. With the skin side facing up, drizzle olive oil over the chicken.
Remove the preheated pan from the oven and place the chicken in the pan, skin-side down.
Place the lemon slices over the bird along with fennel, onions, garlic, thyme and oregano. As it cooks, this will flavor the bird.
Place in the oven and roast for 30 minutes. Remove from the oven, flip the chicken to skin-side up and add half the wine to the pan. Return to the oven and roast until an instant-read thermometer inserted into the joint between the leg and thigh registers 165 degrees F, approximately 30 minutes longer. When the chicken is done, remove from the pan to a serving platter and allow to rest for 15 minutes before carving and plating.
Meanwhile, make a pan sauce. Place the chicken pan over medium-high heat and add the remaining butter and wine. Stir until the butter is melted and the sauce thickens slightly. Pour the pan sauce over the platter of chicken. Serve immediately.