Preheat the oven to 350 degrees. Have two ungreased cookie sheets at the ready.
In a medium bowl, combine the flour, millet, salt, and baking powder. Whisk to combine. Add the olive oil to the bowl. Using a fork, incorporate the oil into the flour mixture. Then, slowly add the water to the dough as you knead the dough with your hand in the bowl. The dough will be very sticky, but continue to knead until it becomes smooth and elastic, about 2 minutes.
Transfer the dough to a lightly floured counter. Using a rolling pin, roll the dough as thin as you can get it, hopefully about 1/8 inch. Cut the crackers into whatever shape and size you like. A pizza cutter or sharp knife will make excellent squares or rectangles. A biscuit cutter or glass is good for circles. Or pull out the cookie cutters!
Lay the crackers on the baking sheets, leaving about 1⁄2 inch between crackers. Gather up leftover dough scraps, reroll, and repeat. Sprinkle the tops of the crackers with coarse salt and any desired toppings. Bake for 15 minutes–then switch the position of the trays in the oven. Bake for 10 to 15 minutes more, or until the crackers are just barely starting to turn golden at the edges.
Crackers stay good in an airtight container for up to 10 days.