Preheat oven to 425º F.
In a cast-iron skillet, heat a drizzle of olive oil over medium-high heat. Add the corn and sauté, mostly undisturbed, until the corn develops brown spots and begins to char. Transfer the corn out of the pan and add the zucchini slices with another drizzle of olive oil. Let zucchini cook undisturbed until golden, then flip slices to brown on the other side. Then remove from the heat.
Meanwhile, spread the flatbread dough on a parchment-lined baking sheet and par-bake the flatbread for about 5 minutes, just until the dough puffs a little and gets a slightly golden color in spots.
Brush the flatbread with olive oil and evenly spread the zucchini slices and corn, then top with pieces of Boursin cheese. Sprinkle with red pepper flakes if desired. Bake the flatbread for about 5-8 more minutes until the crust is golden and the cheese is melted.
Meanwhile, make the optional arugula salad. In a jar, make the vinaigrette by shaking the vinegar and olive oil until emulsified. Add salt and pepper to taste.
Toss the handful of arugula, cherry tomato halves, and minced shallot with the vinaigrette and set aside.
When the flatbread comes out of the oven, slice it into 4-6 pieces and top it with the dressed arugula salad.