Mix together the flour, salt, sourdough starter and the olive oil until it forms a soft dough. ** SEE Note if using 100% Whole Wheat instead of Sprouted Wheat Flour.
Shape and flatten the dough into a rectangular piece about ½ inch thick and wrap in plastic. Let the dough rest in the refrigerator for about an hour.
Meanwhile, make the baking soda wash by combining the baking soda and the boiling water and stirring to dissolve the soda. Let cool.
Preheat the oven to 375F
Roll the dough out on a piece of lightly floured parchment paper until it is 1/16 inch thick. Make sure the dough is of even thickness throughout
Brush the dough thoroughly with the baking soda wash and let it sit for 2 minutes to absorb slightly
Carefully turn the dough over on the parchment, using a rolling pin to help you, and spread out any wrinkles. Brush the 2nd side with the baking soda wash and let it sit another 2 minutes.
Brush the dough with egg wash and liberally sprinkle it with the coarse salt.
Use a knife or a pizza cutter to slice the dough into squares. You do not need to separate them.
Slide the parchment with the crackers on top onto a baking sheet.
Bake the crackers for 20-25 minutes, rotating the pan halfway through baking. Start checking the color at the 15 minute mark. If any of the crackers are getting too dark, just pull those few off of the sheet and continue to bake the rest.
Bake until the crackers are evenly dark and crispy.
Notes
Mary T -- Made these with all 100 % whole wheat flour -- allowing the dough to ferment for 15 hours before rolling it out and making her crackers!! Way to GO Mary!