Prepare Citrus: Zest both lemons into the large mixing bowl. Juice the lemons to yield approximately 3 tablespoons (45 mL) of fresh juice.
Combine Dry Ingredients: To the bowl with the lemon zest, add the rolled oats, chia seeds, hemp hearts, and ground cardamom. Stir briefly to combine.
Create the Liquid Base: In a separate medium bowl or large liquid measuring cup, whisk together the nonfat Skyr, unsweetened soy milk, lemon juice, honey, and vanilla extract until the mixture is completely smooth.
Hydrate the Oats: Pour the liquid base over the dry oat mixture. Use a silicone spatula to fold everything together until no dry spots remain.
Incorporate Fruit: Gently fold in the frozen blueberries. The mixture will begin to take on a soft lavender hue.
Chill and Thicken: Transfer the oat mixture into a large airtight container and seal tightly. Refrigerate for a minimum of 6 hours, or overnight, until thick and creamy.
Assemble and Serve: Once chilled, stir the oats. Divide the mixture evenly among the four glass jars. Just before serving, top with a sprinkle of toasted unsweetened coconut flakes and a few extra blueberries, if desired.