Preheat oven to 225ºF (108°C). Line a baking sheet with parchment paper.
In a small bowl, stir together orange zest into the sea salt. (If you are making multiple kinds of citrus salt, mix each one separately.) Use your fingers or the back of a spoon to work the zest into the salt, making sure to eliminate any clumps of zest.
Spread the salt mixture evenly over the parchment-lined baking sheet. Bake for 60 to 70 minutes, until zest has dried. Let cool. If done, the zest should crumble when you rub it between your fingers.
If a fine salt is desired, place the salt into a food processor and pulse until fine. Store in an airtight container or salt grinder up to 3 months.