Preheat the oven to 325 degrees F. In a medium bowl, stir together the egg white protein, almond flour, baking soda and salt. Cut in the butter using a pastry blender or your fingers until the butter lumps are smaller than peas. Stir in the water to form a stiff dough. Place the dough in a ziplock. Cut a small hole in the corner of the bag. Squirt the dough onto a cookie sheet, making shapes like a pretzel OR cut into cracker shapes. (OPTIONAL: Whip egg yolk in a small bowl, brush the egg wash on the pretzels and sprinkle additional flakey salt on top.) Place pretzels 1 inch apart. Bake for 7-9 minutes in the preheated oven, until edges are lightly browned. Remove from oven to cool.