Preheat oven to 250F/120C
In a large bowl, add oats, nuts, and seeds and stir to combine.
In a large jar or smaller bowl, add maple syrup or honey (or agave), brown sugar, oil, water, vanilla and cinnamon (if using) and stir or shake.
Pour wet ingredients over dry and combine with large spoon
Transfer granola to a large baking sheet lined with parchment paper and pat down lightly (firmly if you would like more chunks/clusters of granola).
If you like a chunky granola, aim for ¼ inch thickness when forming and patting down the granola. Use clean hands to form rectangle shape.
Place tray in center rack of oven and bake for about 1 hour and 15 minutes.
Stir about halfway through baking time (unless you want chucks of granola, then do not stir.)
After baking, allow to fully cool before breaking up into chunks, and add then optional add ins (chocolate chips, dried fruit)
Granola continues to crisp as it's left out in open air, so feel free to leave out for a few hours after it's cooled.
Store in sealed container only after it has completely cooled or the condensation will cause the granola to soften.
Freeze for up to 3 months in a sealed freezer bag with excess air squeezed out of bag.