Preheat the oven to 180°C / 360°F and prepare a loaf tin by greasing or lining with parchment.
Optionally pulse the oat flakes briefly in a blender for a slightly finer texture, then place in a bowl.
Add salt, bicarbonate of soda, pumpkin seeds and sunflower seeds and mix well.
In a separate bowl, whisk yoghurt, egg and apple cider vinegar until smooth.
Pour the wet mixture into the dry ingredients and stir until all the oats and seeds are moistened.
Let the batter rest for 5–10 minutes so the oats hydrate and the mixture thickens.
Transfer the batter to the prepared tin and smooth the surface evenly.
Bake for about 30 minutes at 180°C / 360°F until firm on top and lightly golden.
Cool in the tin for 10 minutes, then remove the loaf and place on a rack to cool completely.
Slice with a sharp knife and serve plain, toasted or with your favourite toppings.