Wash your sea beans well to remove any sand they might have on them.
OPTIONAL STEP: Boil your sea beans in salty water for 1 to 2 minutes, then shock them in a bowl of ice water. This is only for color. The blanching step keeps the salt greener.
Dehydrate between 90°F and 105°F until hard and brittle, about 8 to 12 hours.
Break up the dried sea beans with your fingers, then grind in a spice grinder or a strong blender with a dry blade attachment. Sift the powder to remove any larger bits, and regrind those either in the grinder, or with a mortar and pestle.
Store in a closed container in the dark indefinitely. It will brown slowly over time, so if you don't use it often, keep it in the freezer.
Notes
This recipe makes about 1/4 cup and can be scaled up infinitely.