Place the vegetable slices on paper towels in a single layer; sprinkle with sea salt. Let stand for 15 minutes, then blot dry. Position racks in the upper and lower thirds of the oven and preheat to 375 degrees . Line 2 baking sheets with parchment.
Working in batches, place vegetable slices in a single layer on the baking sheets. Bake until crisp, about 20 minutes; sprinkle with sea salt. Let cool on the baking sheets for 5 minutes. Transfer to a bowl. Wipe the baking sheets clean. Repeat with more cooking spray and the remaining vegetable slices.