Preheat your oven to 350°F (175°C) and line an 8-inch square baking dish with parchment paper, leaving overhang on the sides for easy removal.
In a large mixing bowl, combine almond flour, coconut flour, shredded coconut, granulated erythritol, and salt. Mix these dry ingredients until well combined.
Stir in the melted coconut oil, lemon juice, lemon zest, and vanilla extract until the mixture becomes a coarse, sandy texture.
Fold in the pumpkin seeds, slivered almonds, and poppy seeds until they are evenly distributed throughout the mixture.
Transfer the granola bar mixture into the prepared baking dish. Press it down firmly into an even layer, ensuring it's compacted to help the bars hold together after baking.
Bake in the preheated oven for 20 minutes, or until the edges are golden brown and the center is firm to the touch.
Allow the bars to cool completely in the dish on a wire rack. Once cooled, use the parchment paper overhang to lift the bars out of the dish.
With a sharp knife, carefully slice into 10 equal-sized bars.
Store the bars in an airtight container at room temperature or in the refrigerator for extended freshness.