Put the rosemary leaves and coarse salt(or sea salt or a mix of both) in a food processor.
Pulse until the rosemary is completely blended into the salt, it will take about 7 to 10 times. Pulse until the texture should is similar to table salt. It will look like wet green sand.
If you are using fresh rosemary, spread the mixture evenly over a baking sheet, cover with aluminum foil and leave it out to dry for a fat least 3-4 hours. If you need to speed up the process, you can bake for 20 minutes at 200º F / 95º C.
Once the rosemary salt is dry, put it into a sealed airtight container and store it in a cool and dry place.
Notes
It is better to use fresh rosemary leaves since it will give a stronger flavor than dried rosemary. Use dried rosemary leaves if you are in a rush, or you are out of fresh rosemary. If you use dried rosemary, you'll make your flavored salt in 10 minutes since you can skip the drying process of 4 hours.Coarse salt, since it has bigger granules, is better to use in dishes where adding a salty and flavorful contrast is ideal. Use coarse salt if you are going to sprinkle on top of a steak, pork roast, roasted or grilled chicken, bread, cooked eggs, roasted vegetables like potatoes, fresh tomatoes, avocado toast, etc.