Preheat oven to 375 degrees F (190 degrees C).
In a large bowl, combine flour, 1/4 teaspoon salt and 3 tablespoons sugar. Add oil and milk and mix together. Roll out and line a 9 inch pie pan. Bake at 375 degrees F (190 degrees C) for 10 minutes or until golden brown.
Place 2 cups of fresh blueberries in baked pie shell.
In a saucepan, combine 2 cups fresh or frozen blueberries, water, cornstarch, 1/4 teaspoon salt and 3/4 cup sugar. Bring to a boil and continue to boil for 5 minutes or until thick and clear. Add butter and lemon juice.
Pour filling over berries in pie shell and allow to cool.