In a medium bowl, whisk together chickpea flour and salt. Slowly whisk in about 1/4 cup of the water. Continue whisking until the mixture is smooth. Whisk in the remaining water. Set aside for at least 15 minutes while you chop the vegetables.
Heat one tablespoon of the olive oil in a cast iron skillet over medium-high heat. You can do this on a stove or on a grate set over a campfire. Add the chickpea batter to the hot skillet. Scatter the zucchini, onion and garlic over the top of the flatbread. Drizzle with remaining tablespoon of olive oil. When the batter is almost set, quickly flip the flatbread over and continue cooking until the veggies are browned and the flatbread is set.
Season with more salt and pepper, to taste. Serve immediately.