On a rimmed baking sheet lined with a silicon mat or parchment paper, spread the leaves out in a single layer. Heat the oven to its lowest setting (140 to 160 degrees is ideal), then slide in the herbs and heat them—really it’s dehydrating—until the leaves are dry, about 30 minutes depending on the temperature of the oven. (If your oven has a convection fan, use it here.) Cool. If you have more time, you can also bunch the herbs and wrap the base of the stems tightly with kitchen twine and hang in a dry place for 3-5 days until the herbs are completely dried.
Using a small food processor, electric spice grinder or a mortar and pestle, coarsely pulverize the dried herbs, then mix with the coarse salt.