Preheat oven to 350°F (175°C).
In a pot over medium-low heat, cook the blueberries with lemon juice and maple syrup. Let it simmer for 5-10 minutes until the blueberries soften. Break them up with a fork or spatula. Stir in chia seeds and set aside to cool.
Prepare the dough:
In a food processor or stand mixer, pulse together the almond flour and tapioca flour until well mixed. Add the coconut oil, water, and maple syrup, pulsing until a sticky dough forms. If it’s too dry, add more water. If too wet, add more tapioca flour.
Roll out the dough:
Divide the dough in half. On floured parchment paper, roll out each half to ¼-inch thickness. Cut the dough into six 3×5 inch rectangles. Place them 2 inches apart on parchment paper.
Fill and seal the pop tarts:
Spoon 2-3 tablespoons of blueberry filling onto the dough rectangles, leaving space around the edges. Roll out the other half of the dough, cut into rectangles, and place on top of the filling. Seal the edges using the back of a fork. Optionally, brush with egg wash or melted coconut oil, and sprinkle with coarse sugar.
Bake:
Bake the pop tarts for 12-14 minutes, until the edges are golden brown. Let them cool before icing.
Make the icing:
In a bowl, whisk together powdered sugar, almond milk, vanilla, and the reserved blueberry jam until smooth. Drizzle the icing over the cooled pop tarts and enjoy!