Heat oven to 400 degrees. Line a sheet tray with parchment paper.
Lightly dust your work surface with flour. Roll the sheet of puff pastry out to 12x15 inches, and cut out 12 squares. Brush edges of squares with egg wash. Add a Brie wheel in the center of each. Twist puff pastry up around it, bringing all 4 corners to the top to meet. Twist to secure. Brush outside with egg wash and sprinkle with flaky sea salt.
Place on prepared baking sheet, and bake until golden and puffed, 20 to 25 minutes. Serve with crackers and jam.