Move oven rack to lower-middle position and preheat oven to 350 degrees F.
MAKE ZUCCHINI FILLING:
In a large skillet over medium-low heat, heat oil until shimmering. Add zucchini, shallot, garlic, and salt and cook, covered, until onions are tender and zucchinis have released their liquid, about 7 minutes.
½ Tablespoon olive oil, 2 small zucchinis, 1 large garlic clove, ¼ teaspoon salt, 1 large shallot
Uncover and cook until the bottom of the pan is dry, often stirring, about 4-5 minutes. Transfer zucchini filling to medium bowl, toss with basil and flour and set aside to cool for 5 minutes.