Preheat the oven to 300 degrees.
In a medium saucepan over low heat, add the oil or butter, peanut butter, and maple syrup.
Heat the mixture just until the oil/butter is melted.
Remove from heat.
Stir in the cinnamon, vanilla, and salt until everything is emulsified.
Lastly, stir in the oats and seeds, if using, until the oats are evenly coated.
Pat the mixture into a tight square shape on a cookie sheet (this ensures you will get big clusters as opposed to individual oats, if that is your desire).
Bake for 25 minutes, untouched.
Cool for 15-20 minutes.
Break into clusters and enjoy!