Grease 4 ramekins with cooking spray and place them in the bottom of your slow cooker.
In a large bowl, whisk together almond flour, cocoa powder, erythritol, baking powder, and salt.
In a separate bowl, beat eggs, melted coconut oil, almond milk, and vanilla extract until smooth.
Combine wet and dry ingredients, stirring until just mixed.
Divide half the batter among the ramekins, place a chunk of dark chocolate in the center of each, then top with remaining batter.
Pour 1 cup of hot water around the ramekins in the slow cooker, cover, and cook on high for 2.5 hours.
Carefully remove ramekins and let cool for 5 minutes before serving warm.