Combine the flour and salt, (and fast action yeast if using) in the bowl of a free standing food processor with a dough hook attached. Add the starter to the water, stir to combine, then pour over the flour. Run the machine at the lowest speed for approximately 4 minutes. Turn the speed up and continue for a further 2 minutes. Add the all the seeds and run the food processor for a further 2 minutes on high speed. The seeds absorb a lot of moisture and the dough should now be firm.
Let the dough rest for 30-60 minutes at room temperature. Cover with plastic to prevent drying out and pop in the fridge overnight. (or for up to 48 hours).
Pre-heat the oven to 180°C fan, put a large, flat baking tray in the oven on a low shelf.
Sprinkle wholemeal or rye flour on the work surface and divide into 17 pieces. Then shape into buns. Roll out to approx. 18 cm in diameter. It’s important they’re even in thickness so work carefully to achieve this. Cut out holes in the middle if desired. If you have a Swedish dimpled rolling pin, roll it over each crispbread, if not, prick with a fork, all over the surface. Place four at a time on the hot baking tray, if it's big enough. Bake for 7 minutes, then turn over and cook for another 6-7 minutes. Keep an eye on the first batch, as every oven varies. You may have to adjust the cooking time accordingly. The crispbreads should be golden in colour.
Once you have baked all the crispbreads turn the oven off and leave until it has cooled right down. Place the crispbreads back on the baking tray, it doesn't matter if they're piled on top of one another and return to a pre-heated oven (110°C) and bake for a further 20 minutes. Leave to cool in the oven.
Store the crispbreads in a airtight container. Suitable for breakfast, lunch, snack and as an accompaniment to a cheese board.