Preheat oven to 375°F (190°C).
Roll out the pie crust and fit it into a 9-inch pie dish.
In a large bowl, mix together the berries, sugar, lemon juice, and flour.
Pour the berry mixture into the pie crust, spreading it evenly.
Place the second pie crust over the filling (if using top crust), trimming excess dough and crimping edges with your fingers or a fork to seal the crust.
Sprinkle a small amount of sugar on the crust before baking for added sweetness and a golden, shiny finish.
Make small slits in the top crust to allow steam to escape.
Brush the top crust with a little egg wash (optional).
Bake for 40-45 minutes, or until the crust is golden and the filling is bubbly. If necessary, cover the edges with foil and bake for an additional 10 minutes.
Let the pie cool for at least 1 hour to allow the filling to set properly before slicing.
Serve and enjoy!