1. Heat the oven to 425 F.
2. Place the chicken on the cutting board breast side down. Use sturdy kitchen shears to cut down the length of the spine on both sides. Discard the spine. Turn the bird breast side up. Gripping the 2 cut sides where the spine used to be, open up the bird, pressing down firmly at the centre to flatten it.
3. In a small bowl, mix together the salt, garlic powder, thyme and pepper. Rub the mixture evenly over the entire chicken.
4. Set a large cast-iron skillet on a burner over medium-high. When the skillet it hot, add the chicken breast side down. Let the chicken brown for 5 minutes (or less), then use tongs to carefully flip the bird so the breast side is up. Set the skillet in the oven and roast for 30 to 40 minutes, or until the thickest part reaches 165 F.
For the rub, use:
1TB coarse salt
1TB garlic powder
1/2TB thyme
1/2 TB pepper
Adjust the rub to your liking, I think I’d reduce the garlic powder a bit and maybe try adding some other herbs like Sage?