Preheat an oven to 450 degrees F and prepare a large metal baking tray.
In a mixing bowl, whisk all purpose flour, whole wheat flour, and salt.
Add water and olive oil and stir with a rubber spatula until a dough forms.
Take out a piece of parchment paper roughly the size of your baking tray. With a rolling pin, roll out the dough on the parchment paper as thin as you possibly can. Don't worry about the shape - you can discard irregularly shaped pieces if you don't want to eat them. The most important factor to make sure crackers bake up crispy is how thin you roll it out. Aim for less than 4mm in thickness.
With a pizza cutter or knife, roughly slice the dough into bite size rectangles.
Lightly spray the surface of the dough with your oil spray and sprinkle furikake on top.
Bake for 12-15 minutes or until crackers turn golden brown. Leftovers can be stored in an airtight container at room temperature.