Preheat the oven to 350°F (175°C).
Combine almond flour, cocoa powder, melted coconut oil, maple syrup, and salt in a bowl.
Press the mixture into a 9-inch tart pan, then bake for 12 minutes. Let cool on a wire rack.
While the crust bakes, heat coconut milk until simmering. Pour over chopped dark chocolate and stir until smooth.
Stir in vanilla extract and salt into the melted chocolate mixture.
Pour the chocolate filling into the cooled crust, smoothing the top.
Refrigerate for at least 2 hours, until firm.
Serve chilled, topped with flaky sea salt.