Sieve and mix all three flours together and add the salt, water, olive oil and most of the seeds to make a dough.
Knead the dough very lightly (do not over handle). Roll out half of the dough to 30x30cm square on silicone paper. It may crumble slightly but you can patch up any cracks with the leftover dough. Cut into 6 long strips then across into three strips.
Brush with water and sprinkle over the remaining seeds.
Still on the silicone paper, place onto a baking tray and bake for 15 minutes turning the silicone sheet half way through until the crackers are golden. Repeat with the other half of the dough.
Once cold, break into separate crackers. Place in an air tight container.