Preheat oven to 350 degrees F.
Place parchment paper on a large rimmed baking sheet. Add both types of oats to the pan and spread out. Bake for 7 minutes, to toast them.
Meanwhile, combine olive oil, maple syrup, coconut sugar, vanilla, cinnamon, sea salt in a bowl, whisk together.
Remove oats from oven and pour into a large bowl. Add nuts and flax seed. Then pour liquid mixture over the top and stir to fully coat.
Turn oven down to 300 degrees F. Spread granola onto baking sheet, pressing down to make it stick together in compact form, as one uniform piece that is about 1/2 inch to 1 inch thick.
Bake for 30-35 minutes, until mostly dry. DO NOT STIR. Remove from oven and let cool completely (it will harden as it sits, patience) before breaking it into big chunks.