Preheat the oven to 180° (top and bottom heat). Line a baking tray with baking paper.
Chop the hazelnuts with a knife until they have the desired size. If you like, you can also use whole hazelnuts.
Mix Bircher Muesli, oat flakes, chopped hazelnuts, linseed, cinnamon and salt in a large bowl.
Add vegetable oil and maple syrup and mix well again so that the whole muesli mixture is covered with oil and maple syrup.
Pour the mixture evenly onto the prepared baking tray and spread.
Bake for 10 minutes, then remove from the oven briefly, turn the mixture over with a spoon and bake again for another 10 minutes.
As soon as the granola gets a crispy brown colour, take the tray out of the oven and let it cool down. Attention: During the last few minutes you should keep a good eye on the crunchy granola so that it does not burn.
For serving we recommend (plant based) yoghurt and fresh, diced apples.
For storage, pour the granola into an airtight sealed glass jar. Eat within 2 weeks.