Preparing the clams: the day before cooking, clean the clams by placing them in a bowl of salted cold water for at least 12 hours. Immediately before cooking, rinse the clams under cold water to ensure that all sand has been removed.
Place the rinsed clams, garlic, and white wine in a skillet over high heat. Let the wine evaporate, cover the pan tightly with the lid, and wait until the clams open completely, this should take about 3 minutes. Remove the clams and garlic. Drain the liquid, strain, and reserve.
In the same pan, heat the olive oil over medium heat. Add the garlic and red pepper flakes and sauté for about 1 minute. Return the clams and filtered liquid to the pan and heat for 2 minutes.
Finely chop the parsley and cook the spaghetti in boiling salted water until it is almost al dente.
Drain the spaghetti and add to the pan with the clams. Stir for a few seconds and serve immediately with sprinkled parsley and freshly ground black pepper to taste.