Fire up the wood-fired oven an hour or two before you're ready to cook. When the temperature has reached 180°C, or slightly lower (check your thermometer), and the smoke and flames have died down, you can start cooking. Always keep an eye on the fire and top up the heat source, if needed.
Clean and wash the shellfish, pulling the beards off the mussels and throwing away any open ones.
Peel the garlic and bash with a good pinch of sea salt in a pestle and mortar until creamy, then finely grate in the lemon zest. Add a good pinch of black pepper and pour in enough oil to make a dressing.
Tip the shellfish into a large roasting tray and drizzle with the dressing. Toss everything together, then spread the shellfish out into an even layer.
Halve the lemons, add them to the tray, then slide the tray into the hot oven and roast for 10 minutes or until all the shells have opened and the prawns and scallops are golden and cooked through. Keep an eye on them and rotate the tray for even cooking.
Pick and chop the herb leaves and serve the shellfish straight away, scattered with chopped herbs, and with lots of napkins!