Line an 8x4-inch loaf pan with parchment paper, leaving extra paper hanging over the sides for easy removal.
In a large mixing bowl, whisk together the almond flour, collagen peptides, coconut flour, and sea salt until well combined and lump-free.
In a medium bowl, whisk together the maple syrup, melted coconut oil, lemon juice, lemon zest, and vanilla extract.
Pour the wet mixture into the dry ingredients and stir with a spatula until a thick, uniform dough forms.
Transfer the dough into the prepared loaf pan and press firmly into an even layer using the back of a spoon or a flat-bottomed measuring cup.
Place the pan in the refrigerator for at least 1 hour to allow the bars to set and firm up.
Lift the bars out of the pan using the parchment paper overhang and slice into 10 rectangular bars.
Keep refrigerated in an airtight container for up to 7 days or freeze for up to 3 months.