Scrub the clams under cold water and set aside. In a heavy 3-qt. saucepan, heat 3 Tbs. of the oil over medium heat. Add the pepper flakes and cook briefly to infuse the oil, about 20 seconds. Immediately add the wine, 2 Tbs. of the chopped parsley, and half of the minced garlic. Cook for 20 seconds and add the clams.
Cover and cook over medium-high heat, checking every 2 minutes and removing each clam as it opens. It will take 5 to 6 minutes total for all the clams to open. Transfer the clams to a cutting board and reserve the broth. Remove the clams from the shells and cut them in half, or quarters if they’re large. Return the clams to the broth. Discard the shells.
Bring a large pot of well-salted water to a boil over high heat. Add the pasta and cook until it’s almost al dente, 6 to 9 minutes. Don’t overcook.
While the pasta is cooking, heat the remaining 3 Tbs. olive oil in a 10- or 12-inch skillet over medium heat. Add the remaining 3 Tbs. chopped parsley and the rest of the garlic and cook until the garlic is just soft, about 1 minute. Set the skillet aside.
When the pasta is done, reserve about 1/4 cup of the pasta cooking water and then drain the pasta. Add the pasta, the clams, and the broth the clams were cooked in to the skillet. Return to low heat, toss the pasta in the sauce, and simmer for another minute to finish cooking it, adding a little of the pasta water if you prefer a wetter dish.
Taste for salt and add a large grind of black pepper. Serve immediately, garnished with the parsley leaves.