In a blender, blend all the ingredients until smooth.

Line the base and sides of a slow cooker with parchment paper. Pour the pumpkin mixture into the slow cooker.

With a spatula, smooth the pumpkin mixture to make an even layer. Cover and cook on LOW for 4 hours or on HIGH for 2 hours, until the center is firm.

Turn off the slow cooker and let the pumpkin pie cool to room temperature. Remove the pie, lifting it off the parchment paper. Transfer it with the parchment paper onto a baking sheet.

Refrigerate the pumpkin pie for at least 3 hours, or until completely cooled.

Cut into 16 bars and garnish with powdered erythritol, if desired. Serve cold.