Line an 8×8-inch pan with foil, leaving a 2-inch overhang and spray with cooking spray. In a food processor, combine 1 cup blueberries, oats, dates, almonds, chia seeds, orange zest, and cinnamon; process until mixture is sticky and holds together. Stir in remaining 1 cup blueberries. Press into prepared pan and refrigerate until set, at least 2 hours. Combine confectioners’ sugar and orange juice and drizzle over top if desired. Cut into 16 bars.