Preheat oven to 350 degrees F. Line baking sheet with parchment paper.
Whisk together egg, salt, and water to create egg wash. Set aside. In a small bowl, mix together turbinado sugar and ground cinnamon. Set aside.
Place puff pastry squares on baking sheet. Add a rounded 1 Tbsp of berry jam in the center of each puff pastry square. Take one end of the square and fold over jam to create a triangle.
Use a fork to crimp the edges and seal the pastry triangle closed.
Brush the tops of the pastry triangle with egg wash. Top with sliced almonds and cinnamon sugar mixture.
Bake for 30-35 minutes until puff pastry edges have risen and puff pastry is golden brown in color. Remove from oven and let pastries cool in pan for 5 minutes before transferring to a wire rack to slightly cool. If desired, top with sifted powdered sugar before serving. Enjoy warm or at room temperature.