Position racks in the upper and lower thirds of the oven and heat the oven to 425°F. Line two large rimmed baking sheets with parchment.
On a floured surface, pat the dough into a 5-inch square. Using a floured rolling pin, roll the dough into a 14-inch square, lightly dusting with flour as you roll to keep the dough from sticking, if necessary.
In a small bowl, beat the egg with 1 Tbs. water. In another small bowl, combine the pecans, seeds, and salt. Lightly brush the dough with the egg wash, then evenly sprinkle with the nut-seed mixture. Using a sharp knife, pastry wheel, or pizza cutter, cut the dough into forty-nine 2-inch squares. Using a spatula, transfer the squares to the prepared sheets, arranging them about 1/2 inch apart.
Bake until golden-brown, 18 to 20 minutes, swapping positions and rotating the sheets halfway through baking. Transfer to a wire rack to cool. (These crackers taste best when freshly made, but they can be frozen in an airtight container for up to 3 weeks. Thaw in the refrigerator overnight and warm in a 350°F oven for 5 minutes before serving.)