Line a standard baking sheet with parchment paper or a silicone mat. Set aside in a cool, dry area.
Place 8 oz of the chopped white chocolate in a microwave-safe bowl. Microwave at 50% power in 30-second intervals, stirring between each, until about two-thirds melted. This should take 1.5 to 2 minutes total.
Remove from microwave and stir in the remaining 4 oz of chopped chocolate. Continue stirring until completely smooth and melted. The residual heat will melt the remaining pieces, creating a light temper.
Pour the melted chocolate onto the prepared baking sheet. Use an offset spatula to spread it into an even layer about 1/4-inch thick, leaving a 1-inch border around the edges.
Working quickly, gently press the edible flowers into the chocolate surface in a decorative pattern. If using raspberry powder, sprinkle it lightly over sections and use a toothpick to swirl.
Sprinkle with flaky sea salt if desired. Refrigerate for 15-20 minutes until completely firm and set.
Once hardened, break the bark into irregular pieces by hand or use a sharp knife to cut clean geometric shapes. Store immediately in an airtight container.
