Grease 4 4-ounce (115 g) ramekins with coconut oil and set aside.
In a medium saucepan over medium-low heat, combine the coconut cream, sugar, and matcha powder. Warm slowly, stirring occasionally, until the sugar is dissolved and the mixture is simmering.
Add the agar agar to hot water and stir until there are no lumps and the agar agar is fully dissolved.
Pour the agar mixture into the warm coconut cream and whisk to combine. Increase the heat to medium, bring to a gentle boil, and whisk continuously for 3 minutes, until thickened. Remove from the heat and immediately divide between the greased ramekins.
Refrigerate for at least 30 minutes. (The agar will set at room temperature, but chilling the panna cotta in the fridge will expedite the process.)
When ready to serve, use an offset spatula or butter knife to carefully work around the edges of the ramekins to loosen the panna cotta. Invert onto serving plates and garnish with coconut flakes.