Spray the slow cooker insert with non-stick cooking spray or line with parchment paper.
In a large bowl, whisk together the pumpkin puree, eggs, melted coconut oil, and vanilla extract until well combined.
In a separate bowl, mix together the cocoa powder, almond flour, sugar-free sweetener, baking powder, cinnamon, and salt.
Add the dry ingredients to the wet ingredients and stir until just combined, being careful not to overmix.
Pour the batter into the prepared slow cooker and spread evenly.
Cover and cook on low for 3 hours, or until the edges are set and the center is just slightly jiggly.
Turn off the slow cooker, remove the lid, and let the cake cool for 20 minutes before serving.