Lightly oil an 8 by 4-inch loaf pan or line it with parchment paper for easy removal. For the first layer, whisk together the coconut milk, water, sugar, agar-agar, and salt in a pot over medium-high heat.

Bring the mixture to a boil, then immediately lower to a simmer for 5 minutes until the flakes and sugar have fully dissolved. Stir frequently to prevent the coconut milk from boiling over.

Pour the mixture into the prepared pan and let it sit at room temperature for about 45 minutes to an hour. Test the firmness by tapping the top; it should be nearly set before adding the next layer.

Make the second layer by whisking coconut water, agar-agar, and sugar in the same pot. Simmer for 3 minutes until clear and dissolved, then let it rest for two minutes before gently pouring it over the first layer.

Sprinkle coconut flakes over the top and allow the entire dessert to set completely for at least one hour. You can speed this up by placing it in the refrigerator.

Once firm, unmold and cut into slices for serving. The jelly is most refreshing when served cold.