Preheat oven to 325°F (160ºC). Place almond flour, walnuts, flax meal baking powder and salt in food processor; pulse to combine. Add egg, rosemary and oil; pulse until mixture forms a ball.
Place dough ball between 2 large sheets parchment paper (about 16 x 12-in./40 x 30-cm) and roll to 1/8-in. (3-mm) thickness. Lift dough -- still inside both parchment sheets -- onto baking sheet. Remove top sheet of parchment. Leaving dough on bottom parchment, use a pizza cutter to score dough into 2-in. (5 cm) squares.
Bake 18 to 20 min. until crackers are set and golden around edges. Turn oven off; leave door ajar and let crackers continue to crisp in oven 10 min. Cool completely on wire rack. Break into squares. Store in airtight container.
Serve crackers on cheese tray. Delicious with aged Cheddar cheese and Serrano ham.
Freeze dough for up to 3 months.
Crackers will keep in an airtight container for up to 3 days.