Put the zucchini on a baking sheet sliced side up and bake them in a pre-heated oven until they start to brown.
Drain any moisture from the baking sheet when you remove them from the oven and pat the sliced surface dry with toweling before you layer on the pizza ingredients.
Start with a thin layer of tomato paste and then add the mozzarella, ham, and basil leaves.
Place the baking sheet with the zucchini pizzas back in the oven until the cheese browns.