Preheat the oven to 350ºF. Spread oats on a baking sheet and toast in the oven 10-15 minutes. Let cool long enough to handle.
Meanwhile, place cashews in a food processor and pulse until chopped into very small pieces but not powdery. Transfer to a large bowl.
Add dates to the food processor (no need to clean it out!) and allow the motor to run until the dates form into a sticky ball. If they are too dry, add a few drops of water and continue to process until the desired consistency is reached. Transfer the dates to the bowl with the cashews.
In a glass measuring cup, stir together maple syrup, cashew butter, and salt. Add to the bowl with the cashews along with the cooled oats. Stir everything together until well combined, using your hands if necessary.
Transfer the mixture to an 8x8 pan lined with parchment and use your hands to press it into a firm square. Place in the freezer until solid, then remove from the pan and cut into squares. I like to keep the granola bars in the freezer until ready to eat. They should keep for several months. Allow to come to room temperature before eating, then top with additional cashew butter, almond butter, chocolate chips, or melted chocolate if desired.