Line a large baking sheet with parchment paper or a silicone mat. Set aside in a cool, dry area away from any moisture.

Place the white chocolate in a microwave-safe bowl. Microwave at 50% power in 20-second intervals, stirring thoroughly after each burst, until the chocolate is 90% melted with just a few small pieces remaining. The residual heat will finish melting them as you stir.

Stir the chocolate until completely smooth and fluid, ensuring no lumps remain. If needed, microwave for one final 10-second burst at 50% power.

Pour the melted chocolate onto the prepared baking sheet. Use an offset spatula to spread it into an even rectangle about 1/4-inch thick, leaving a 1-inch border around the edges.

Immediately sprinkle the freeze-dried blueberries evenly over the surface, pressing some gently into the chocolate while leaving others on top. Sprinkle with sea salt flakes if using.

Tap the baking sheet firmly on the counter 3-4 times to release air bubbles and settle the toppings.

Refrigerate for 20-30 minutes until completely firm and set. Do not freeze, as condensation can affect the texture.

Once set, break the bark into irregular pieces using your hands or a sharp knife. Store immediately in the refrigerator in an airtight container with parchment between layers.