In a large bowl, mix the oats, seeds, and nuts together. Stir in the pumpkin pie spice, vanilla, canola oil, maple syrup, and salt until it's all well combined.
Spread the granola mixture onto a large, parchment-lined baking sheet so it's in a thin layer.
Bake at 300F for 10 minutes, then stir it. Bake for 10 more minutes, then stir it again. Bake for 3 more chunks of 5 minutes each, stirring each time. When the edges of the granola in the pan are a darker brown and it starts to smell roasty, take it out of the oven and mix it one more time.
Once it's out of the oven, stir in the raisins (if using). Leave it to cool on the tray. It will crisp up nicely. Cool completely, then store it in an airtight container in your cupboard. Enjoy!