Adjust oven rack to middle position and heat oven to 425 degrees. Stir almond flour, Parmesan, whole egg, oil, sesame seeds, poppy seeds, caraway seeds, and table salt together in bowl. Press and roll dough between 2 sheets of greased parchment paper into 11 by 9- inch rectangle, about ⅛ inch thick. Remove top piece of parchment and trim edges to remove any tapering.
Slide dough, still on parchment, onto baking sheet. Brush with egg white mixture, then poke at 2-inch intervals using fork. Sprinkle with sea salt, if using. Bake until dough is set and edges are beginning to brown, about 7 minutes, rotating sheet halfway through baking. Slide cracker, still on parchment, onto cutting board. Reduce oven temperature to 350 degrees.
Cut cracker lengthwise into four even strips, then cut crosswise into 1-inch-wide crackers. Carefully arrange crackers evenly on now empty sheet, discarding parchment. Bake until golden brown and crisp, 4 to 6 minutes, rotating sheet halfway through baking. Transfer crackers to wire rack and let cool completely, about 30 minutes. Serve