Preheat your oven to 375°F and line two baking sheets with parchment paper.
In a small bowl, combine olive oil, minced garlic, rosemary, thyme, salt, and pepper. Let it sit for 5 minutes to let the flavors meld together.
Arrange baguette slices in a single layer on the prepared baking sheets.
Using a pastry brush, generously brush the herbed oil mixture onto each bread slice, making sure to get some of those garlic and herb pieces on each one.
If using Parmesan, sprinkle a small amount over each crostini.
Bake for 10-12 minutes, until golden brown and crispy around the edges. Keep an eye on them after 8 minutes—they can go from perfect to burnt quickly!
Let cool for 5 minutes before serving. These can be made up to 2 days ahead and stored in an airtight container.