01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a small saucepan, combine the blueberries, maple syrup, and lemon juice. Cook over medium heat, stirring frequently and gently mashing the berries, until they soften and release their juices, about 5 minutes. Stir in the cornstarch if a thicker consistency is desired. Remove from heat and let cool slightly.
03 - In a small bowl, whisk together the ground flaxseed and water. Let the mixture rest for 5 minutes until it thickens into a gel-like consistency.
04 - In a large mixing bowl, whisk together the rolled oats, all-purpose flour, baking soda, salt, and ground cinnamon until evenly distributed.
05 - In a separate bowl, blend the melted coconut oil, brown sugar, unsweetened applesauce, prepared flax egg, and vanilla extract until smooth and well incorporated.
06 - Pour the wet mixture into the dry ingredients and stir gently until just combined. Fold in the raisins, being careful not to overmix.
07 - Drop heaping tablespoons of dough onto the prepared baking sheets, spacing each portion approximately 2 inches apart to allow for spreading.
08 - Using a small spoon, place about 1 teaspoon of the blueberry mixture onto each cookie. Gently swirl it into the dough using a folding motion to create a marbled effect.
09 - Bake for 12 to 14 minutes, or until the edges are golden and the centers appear set. Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.