I grew up bouncing back and forth between New York and Boston, which, conveniently, put me right in the path of the pizza behemoth known as New Haven, home to some of the world's finest pizzas (or apizza in the local vernacular, pronounced uh-beets), and originator of the clam pie.
Now, at most of the great pizzerias in that neck of the woods—Pepe's, Sally's, and Modern being the big three—fresh clams have taken a back seat to pre-shucked clams. Don't get me wrong, the pies are still great. I love the way the clam juice leaks around and mixes up with the cheese, olive oil, herbs, pepper flakes, and garlic that are standard on a clam pie. But something certainly gets lost when the clams are pre-shucked. Need proof? Just visit Zuppardi's in West Haven, where the clams are shucked fresh to order before being spread onto the pies. The flavor is better, the clams are juicier; it's just a better eating experience.
Clam pizza is the kind of pie that you need to start eating immediately after it's cut into slices, before the copious clam juices have a chance to render the crust completely soggy (though some degree of sogginess is inevitable—some people even consider it a feature).
Even so, roasting a clam in the open heat of an oven is still not the ideal way to do it, even if its been freshly shucked.
Want to know the secret to the absolute tenderest, most flavorful clams and juiciest clam pizza around? Place the whole, unshucked clams on that pie before baking. It may look strange at first, and it will definitely look strange when it comes out of the oven, but the clams will be insanely tender and you won't lose a single drop of those precious juices.
I place the clams on the pie with their hinges pointed down, and then bake the pie as I normally would (in this case I did it on my KettlePizza-converted grill). If all goes well, and there's no reason it shouldn't, the pizza will finish baking just as the clams start to crack open, spilling their juices over the top of the pie.
You can serve the pie as-is and let people pull out their own clams as they eat, but I prefer to be nice about it and finish prying the little guys open, shucking out the meat, and depositing them, along with their juices, into the wells left behind from the shells.