Mix the flour and salt together in a large bowl.  Add the butter and cut it in with a pastry blender until the largest pieces are the size of small peas and the mixture begins to clump on the pastry blender.

Sprinkle the water over the mixture and stir with a fork.  Squeeze a clump of dough together in your hands.  If it holds its shape it is just right.  If it is still crumbly and does not hold together easily, add another tablespoon or two of ice water until you can squeeze a handful, and it holds together.  

Divide the dough in half and form each half into a flat disk.  Wrap each disk in plastic film and refrigerate for at least 30 minutes. 

Remove the dough from the refrigerator and let it rest at room temperature to soften up a little and make it easier to roll.

Preheat the oven to 450°F

Add the berries to a large bowl.  Drizzle the lemon juice over the berries and toss to combine.

In a small dish, add the sugar, clear jell (or tapioca), and salt.  Sprinkle the mixture over the fruit and gently fold together to coat well.

Roll out one of the pastry disks for the bottom crust to a diameter of about 14 inches. Carefully fit the pastry into a 9-inch, deep-dish pie plate.

Spoon the fruit mixture into the pie crust and dot with the butter bits.  

Roll the remaining pastry disk for the upper crust a little larger than 14 inches. Cover the berry mixture with the pastry, trim and crimp the edges together, and cut 4 vents to allow steam to escape.  Brush the top with the egg wash and sprinkle coarse sugar over the top of the pie.

Set the pie on a parchment-lined sheet pan to catch any drips and transfer the pie to the lower position of the oven.  

Transfer the pie from the oven to a wire rack to cool, then refrigerate for 2 to 3 hours or until completely cold. If you slice the pie while it is still warm, the juices will run. If you want warm pie, you can zap the slices in the microwave after you slice it.