Begin by placing the whole chicken breast-side down on a cutting board. Using poultry shears or a sharp knife, carefully cut along each side of the backbone to remove it. Once spatchcocked, flip the chicken over so the breast side faces up and gently press down to flatten it. Allow the chicken to come to room temperature for about 30 minutes before roasting.

In a small bowl, combine 2 tablespoons of olive oil, smoked paprika, kosher salt, and black pepper. Rub this mixture generously all over the chicken, including under the skin.

Preheat your oven to 400°F (200°C).

In a large bowl, toss the baby potatoes, carrots, parsnips, and fennel with the remaining tablespoon of olive oil, thyme, salt, and pepper. Arrange these vegetables around the flattened chicken in a cast iron skillet or a rimmed baking sheet.

Place the skillet in your preheated oven and roast for about 45 minutes to 1 hour until the chicken's internal temperature reaches 165°F.

Once cooked, remove the skillet from the oven and let the chicken and vegetables rest for 10-15 minutes before carving.