Mix the oats and flour with 600 ml (approximately 2 cups) of lukewarm water in a bowl. Cover and let soak for 1 hour.
Preheat the oven to 180°C (approximately 350°F). Line a baking sheet with parchment paper.
Chop the sunflower seeds coarsely. Add the sunflower seeds, sesame seeds, flaxseed and salt to the oat-flour mixture. Mix well and spread thinly over the lined baking sheet. Bake in the preheated oven for about 15 minutes. Remove from the oven and break or cut into pieces. Spread the pieced on the baking sheet and bake in for 40-45 minutes. Remove from the oven and cool completely on a wire rack before serving.