Mix flour with about 1/2 cup cold clam juice or wine, and then stir into the bubbling sauce, stirring constantly, until sauce thickens. Turn heat down to low, and add clams and cook over low heat for 5 minutes to gently heat clams. You may need to add more clam juice or a little pasta water.
This is a light, delicious clam sauce in a white wine sauce. I used 1/2 of a very large (51 oz) can of chopped clams, which I bought at a warehouse store, and a moderately good white wine. I used the hollow tubed thick spaghetti, perciatelli, so the flavor of the sauce permeates the pasta.
Add salt, pepper, and parsley and stir. If serving over pasta, cook the pasta al dente and reserve some of the pasta water. Add the cooked pasta to the reduced clam sauce and then add a few splashes of the pasta water to help the sauce thicken.
Spoon the sauce over the pizza crust, sprinkle with cheese, and bake until the cheese is melted, about 5 to 8 minutes. If you want a more authentic flavor, add 1/4 cup of white wine when you add the clams. The wine will reduce and add richness to the dish.