Preheat the oven to 180°C/fan 160°C/gas mark 4.
Peel the potatoes and chop into 5cm pieces. Rinse well to remove the starch.
Place in a pan and cover with cold salted (5g of salt per litre) water. Bring to a simmer without boiling hard and simmer gently for 12 minutes until cooked through and crumbling at the edges. Stir the pan gently a few times while cooking.
Drain the potatoes in a colander, lay them in a single layer on a tray and allow to steam dry.
Pour 2-3 tbsp of the olive oil into a roasting tin. Sprinkle on a large pinch of sea salt. Arrange the potatoes in the tin in a single layer.
Lay the garlic cloves on a board and bash gently with the flat of a knife, just enough to split the clove. Tuck the cloves in between the potatoes. Trickle over another 4 tbsps of olive oil and another pinch of salt.
Roast in the oven for 30 minutes.
Take the tin out and turn the potatoes. Baste them with the oil in the tin adding more if needed. If any of the garlic cloves are blackened, remove them. Return to the oven for a further 20-30 minutes.
10 minutes before the end tuck in the sprigs of rosemary and thyme.
Remove from the roasting tin and serve with a sprinkling of black pepper and fresh thyme.