Use a suitable amount of fine and clean bladderwrack.

The seaweed should be rinsed thoroughly before use to remove sand and other impurities.

Place the seaweed on a piece of parchment paper on a baking sheet.  

Put the tray in a 100 degrees Celsius (212 degrees Fahrenheit) oven and let the seaweed dry for 30-45 minutes. It should be bone dry.

Remove the tray from the oven and let the seaweed cool.

Mix the dried seaweed with sea salt/flake salt and grind the mixture in a mortar. Alternatively, you can use a food processor or electric spice grinder.

Store the seaweed salt in a dry and cool place, preferably in a glass jar with a lid.