To make the granola: Preheat the oven to 300 ̊F (150 ̊C, or gas mark 2). In a bowl, toss together the oats, pecans, and salt. In a separate bowl, whisk together the maple syrup, walnut oil, and vanilla extract. Pour into the oat mixture and stir until the oats are well coated.
Spread the oats on a baking sheet and cover with wax paper. Using your hands or a rolling pin, press down on the granola to spread it evenly across the baking sheet. Remove the wax paper. Bake for 40 to 50 minutes, rotating the pan halfway through baking. The granola should be golden and starting to brown around the edges. Remove the pan from the oven and let cool completely on the pan.
Once the granola is cool, break it into pieces and store in an airtight container at room temperature for up to a week.