Preheat the oven to 220°C conventional or 200°C fan-forced.
Place the whole baby potatoes in a saucepan, cover with cold water and add a generous pinch of salt. Bring to the boil and cook for about 20 minutes, until the skins begin to crack and a fork slides easily through the centre.
Drain thoroughly and leave the potatoes to steam-dry and cool for at least 20 minutes.
Place a heavy baking tray or cast-iron skillet in the hot oven and preheat it for 20 minutes.
Carefully remove the pan from the oven. Add 2 tablespoons olive oil and tilt the pan to coat the base. Arrange the potatoes in a single layer.
Gently press each potato with a potato masher until the skin splits and the potato is approximately 1–2 cm thick.
Spread the garlic, rosemary and thyme around the pan. Drizzle the remaining 2–3 tablespoons olive oil over the potatoes and herbs, then season with salt and black pepper.
Roast for 20–30 minutes, flipping the potatoes after 10–15 minutes. Continue roasting until both sides are deeply browned and the cracked edges are crisp.
Finish with another pinch of salt and serve immediately.