Preheat the oven to 375°F(190C°). Line baking sheet with parchment paper or silicone baking mat. Set aside.
Mix the flour, sugar and salt in a medium bowl. Add in the olive oil and water and mix very well with a spatula until you have a soft and a little bit sticky dough. Although it will be little sticky, you are going to roll it out very easily. Alternatively, you can use your stand mixer with a dough hook attachment at medium speed and do the same steps.
Divide the dough in half. Lightly flour the work surface and the rolling pin, so the dough don’t stick to either. Sprinkle some flour over the dough. Roll out the dough 13*8 inches (34*20cm) long, ⅛ inch (3mm) thick. You can use a cookie cutter and cut out 3 inch (8cm) circles or you can cut into squares using a sharp knife or pizza cutter. If you use a cookie cutter, roll out the dough again with the leftover doughs until no dough remains to roll out. Place the circles on the baking sheet. Prick the dough with a fork to prevent puffing. Slightly brush the dough with water and sprinkle the mixure of nigella and sesame seeds. (While you are placing the doughs on the baking sheet, the shape of the circles may change a little bit. If you want the shape to stay as you cut, alternatively you can roll out the dough on a parchment paper or on a silicone baking mat.)
Bake for 10 to 12 minutes or until the edges become golden brown. Check the oven after 5 minutes. If the dough is puffing, use your fork to prick small holes again. When you turn off the oven, let them stay there for 5 minutes or until the top of the crackers turn golden brown. Remove the baking sheet from the oven and let them cool on the baking sheet. The crackers will shrink while baking up to 0,2 inches (0,5cm) which is normal.