Place the vongole in a large bowl of water, generously salted with sea salt. Let them soak for 2 hours to expel any sand, then filter with a colander to drain and set aside.
Pour a generous amount (6–8 tablespoons) of EVOO into a large pan over low heat, then grate the garlic directly on top, add half of the chopped parsley and cook for 30 seconds stirring gently with a wooden spoon.
Add the vongole stir to coat them in the garlicky oil. Turn the heat to medium-low, then add one ladle of water and a small teaspoon of sea salt.
Cover the pan with a lid, or use foil if the pan is too large, and cook for 5 minutes. You’ll know they’re ready when you don’t hear the vongole opening anymore.
Remove the cover, give the vongole a mix, and pour the contents through a colander set over a bowl to catch the sauce. Set the vongole and filtered sauce aside.
Bring a large pot of water to a boil, add rock salt, allow to dissolve and cook the spaghetti according to the packet instructions.
Wash the pan and return it to very low heat. Pour the filtered sauce back into the pan. Cut the lemon in half, squeeze one half into the pan (catching any pits with your hand), and stir gently to combine.
Set aside 1 mug of pasta water when the pasta is almost ready, and use tongs to transfer the (now) cooked pasta directly into the pan with the sauce. Toss or mix briskly, adding a splash of reserved pasta water as needed.
Return the vongole to the pan and squeeze in the remaining half of the lemon. Add more pasta water if needed to emulsify further.
Drizzle with EVOO, sprinkle with some of the reserved parsley, and toss everything together until well combined.