Preheat the oven to 170°C (340°F) and line a large* baking sheet with parchment paper.
Add the flour, sesame seeds, sunflower seeds, chia or flax, and salt to a large mixing bowl. Stir well to combine.
120 grams whole grain spelt flour, 50 grams sesame seeds, 50 grams sunflower seeds, 40 grams chia OR flax seeds, ½ teaspoon sea salt
Add the water and olive oil and mix until the dough is combined. It will be rather loose and wet.
200 ml water, 2 tablespoons olive oil
Transfer the dough to the prepared baking sheet and spread into a thin, even layer. Use a wet spoon or spatula for this and try to make sure it's not thicker in the middle. Top with a little extra salt at this point if you'd like.
Bake for 40-45 minutes, turning the baking sheet once after 20 minutes. The cracker should be evenly golden and be firm and dry to the touch when finished.
Remove the baking sheet from the oven and set onto a wire rack to cool fully. Once cool, break the crackers up into the sizes you'd like and store in a sealed container at room temperature for up to a week. Seed crackers freeze well.
Notes
All of the seeds should be raw and unsalted. Any colour of sesame and chia or flax can be used.Add extra herbs or spices to the dough if you'd like.* Mine are the standard GN1/1, or 65x53cm (about 26x21 in.). If yours are smaller - like a half sheet - you'll want to divide the cracker dough onto two baking sheets.