Line two or three baking sheets with parchment paper. When I use baking sheets the size of my oven than I only need two. If you're using baking trays you might need three.
Mix sunflower seeds, hemp seeds, and sesame seeds. Set 50 g / 1,8 oz of the mixture aside for the topping.
Mix the seeds with the linseeds, rice flour, salt, paprika powder and nutritional yeast.
Combine with water and oil, and set to rest for 15 minutes. The batter will firm up a bit, but still be runny.
Divide the batter in a thin layer among the baking sheets and smooth out using a spatula or the back of a spoon.
Sprinkle the remaining mixed seeds over the batter.
Bake in the oven for 15 minutes, then carefully cut into small squares or rectangles.
Place back in the oven and bake for another 30 minutes until the edges are browned.
Remove from the oven and check if all the crackers are crisp and browned. For me, the ones in the middle of the baking sheet need longer baking, so I bake them for a couple more minutes (only the ones that are still a bit soft).
Leave to cool completely.
You can store the crackers in an airtight tin for a week.
You can buy whole linseeds and grind them in a nut or coffee grinder.