In a medium saucepan over medium heat, slightly melt the peanut butter with maple syrup.
Add ground cinnamon and salt flakes, and mix everything together.
Add the old fashioned oats, and mix until the oats are well coated.
Press the mixture onto a greased cookie sheet, and bake at 160°C (320°F) for 20-15 minutes flipping halfway through. To know if the granola is done, take a piece out of the oven and let it cool. If it hardens within a few minutes then it's ready, if not then bake for a few minutes longer.
If your granola feels a bit too soft on the next day, just pop it back on a baking tray and bake on low temperature for a few minutes. You need the granola to dry and make sure that you get rid of any moisture left.
Store in sealed jars at room temperature for up to 4 weeks.