Slice the baguette into ½-inch rounds. Heat a large skillet over medium heat and drizzle with olive oil. Add the baguette slices, drizzle with a little more oil, and cook for 3 minutes per side until golden and crispy. (Oven method: arrange slices on a baking sheet, brush with olive oil, and bake at 400°F/200°C for 8–10 minutes, flipping halfway.)
While the crostini toasts, slice the tomatoes and mozzarella into thin rounds. Tear or stack the fresh basil leaves.
Arrange the toasted crostini on a serving platter. Layer each piece starting with a slice of fresh mozzarella, then a slice of tomato, then a basil leaf.
Season generously with salt and pepper.
Drizzle generously with balsamic glaze right before serving. Enjoy immediately!