Collect Sea water (the cleaner the sea the better)
Pour into a pot through a cheesecloth.
Bring the pan to a boil and reduce the water till there is only a little left. (Don't boil till its dry as you might burn the salt and your pan)
Leave in a warm oven over night. Then your salt is ready to be used or you can add herbs and spices to it. Great as Christmas presents for keen cooks.