Clean blueberries and weigh in grams. Multiply weight of blueberries by .03 to calculate how many grams of salt is needed.
Place blueberries and salt in a vacuum sealable bag and shake well to distribute the salt. Carefully spread berries out then remove air and seal bag.
Store at room temperature and allow the bag to become fully pressured/puffed up (3-10 days). At that point, they’re ready. Transfer to jar and refrigerate. Use within a month for best flavor (they become sourer with age).