Preheat oven to 350ºF. Line a baking sheet with parchment paper.

Use a vegetable peeler to peel carrot ribbons in uniform thickness. (I've found it's easiest to place the carrots on a cutting board and use a bit of pressure when creating the ribbons.)

Place carrot ribbons in large bowl and toss with the olive oil and rosemary.

Transfer the carrots to the prepared baking sheet in a single layer; the edges can be touching, but don't overlap them. Sprinkle with sea salt flakes.

Because peelers and oven temperatures both vary and you're working with thin strips of carrots, you'll have to keep an eye on your crisps. Check them after 10 minutes and then every 5 minutes after that. They're done baking with they're just beginning to brown and curl on the edges.

Place the baking sheet on a wire rack to cool until carrots are crisp, about 5 minutes. Serve immediately.