Put the coquelet with the breast side down the cutting board.
Use a pair of kitchen shears to cut the backbone out by run the shears up each side of the spine, starting from the tail up.
Turn the coquelet with the breast side up and press the breast down firmly with your hands to flatten it. You should hear the breastbone crack, that's your cue that you got it.
Seasoning
Take a small bowl and add the olive oil, salt, pepper and paprika, then mix thoroughly.Rub the chiken with half of the mix inside-out (focus on the outside, of course).
Wash and drain the potatoes and the garlic heads. Cut the potatoes in quarters lengthwise (skin-on) and the garlic in halves width-wise (skin-on).
Rub the potatoes with the remaining seasoning mix and add to a tray.
Add the garlic halves, lemon slices and rosemary stems to the tray.
Gently pour the chicken stock to the tray while being careful not to wash away the seasoning from the potatoes.