Place 4 large (240ml) or 6 small (180ml) ramekins on a sturdy tray, evenly spaced for easy handling.

In a saucepan, combine water and caster sugar, dissolving over low heat. Raise heat to medium-high and cook until deep amber. Quickly pour into ramekins to harden.

In a separate saucepan, whisk almond milk, caster sugar, cornflour, and agar-agar over low heat. Add vanilla pod, coconut milk, vanilla extract, and sea salt. Simmer for 5 minutes until thick.

Pass custard mixture through a fine sieve into a bowl to remove lumps. Cool at room temperature for 20 minutes, whisking occasionally.

Pour cooled custard over hardened caramel in ramekins. Smooth tops, cover with plastic wrap, and refrigerate for 8-12 hours to set.

Run a sharp knife around ramekin edges. Invert onto serving plates to release flan with caramel flowing over it.