The potatoes cook in rendering thigh fat and are better than the chicken. A weeknight dish with one tray to wash.
It helps and it is not essential. Ten minutes while the oven heats is better than nothing.
Potatoes, onion, garlic, oil, oregano and a good pinch of salt tossed together in the largest tray you own. Spread them out so they are touching but not stacked.
This is the single decision the dish rests on. Piled up they steam and go grey; in one layer they roast.
Arrange them over the potatoes with a little space between. Season the skin with pepper.
Pour the stock into a corner of the tray so it runs underneath — not over the chicken. Anything landing on that skin will stop it browning.
210 °C, forty-five minutes, and do not stir, turn, baste or open the door. Every one of those things is a way of making it worse.
The thigh fat renders downward through the whole tray. The potatoes directly under the chicken will be the best ones and there is nothing to be done about that.
Ovens vary. If the skin is golden rather than deep brown at forty-five minutes, five minutes under a hot grill will finish it. Watch it — the gap between deep brown and burnt is about ninety seconds.
Squeeze the lemon over the whole thing while it is still fizzing. Five minutes to settle. Squeeze the roasted garlic cloves out of their skins and mash them into the potatoes.
The tray was too small. Crowded vegetables release moisture faster than the oven can drive it off, the tray fills with steam, and nothing browns — you have effectively boiled them in a hot box.
Use two trays rather than one crowded one. It is more washing up and it is the difference between the dish working and not.