Position a rack in the lower third of oven; place a pizza stone on rack. Preheat oven to 500 degrees at least 30 minutes before cooking.
Heat olive oil in a large pot over medium-high heat. Add onion, garlic, and bay leaf; cook, stirring, until vegetables are soft and fragrant. Add wine and cover pot; bring liquid to a boil. Add clams, cover, and cook, until clams have opened, about 5 minutes. Remove clams from pot and let cool. Remove clams from shells, discarding shells; set aside.
Strain liquid into a medium saucepan; discard solids. Cook liquid over medium-high heat until reduced and thickened. Add cream and continue cooking until reduced and thickened. Remove from heat and let sauce cool.
Divide dough into six equal pieces; shape one piece into a 10-inch-round on a pizza peel or the back of a baking sheet. Spoon just enough of the clam sauce over pizza to cover. Top pizza with 9 clams and sprinkle with pepper flakes.
Carefully transfer pizza to pizza stone and bake until pizza is crisp and nicely browned. Sprinkle with chopped parsley and serve immediately; repeat process with remaining dough and toppings.