Pour milk and oats into a pot over medium heat and mix to combine. Stir in chia seeds, ground flax seeds, and hemp seeds. Bring oatmeal to a soft boil; reduce heat and cook until slightly thickened, about 5 minutes.
Pour oatmeal into a glass dish with an airtight lid. Stir in blueberries. Refrigerate until completely cooled before cutting into bite-sized pieces, about 1 hour.