1. Preheat oven to 350°F.
2. Line a baking sheet with parchment paper, and spread the pecans and oats out on it in a single flat layer. Bake in the preheated oven for 10-15 minutes, until toasted and fragrant.
3. Keep the oven preheated to 350°F. Line an 8" square pan or a 12" x 5 1/2" biscotti pan with parchment paper, leaving enough parchment on the sides to use as "handles" for pulling out the finished bars.
4. Place the toasted nuts and oats in a food processor along with the dates, cinnamon, and salt. Process until the mixture is coarse and crumbly, with no large pieces remaining. Add the chopped apple and pulse in until there are no longer any large chunks left. Continue to process until everything starts to clump together, using a spatula if necessary to help move things around. This process may move slowly, but eventually everything should come together.
5. Transfer the mixture to the prepared pan, using a wide, flat spatula to pat it down into a flat and compact layer that takes up the entire space of the pan. It helps to fold the extra parchment on the sides over the bars, and flatten with the spatula on top of the parchment (to prevent sticking). Be patient with this; the bars will look the exact same once they're done baking, so try to make them really flat and even.
5. Bake the bars in the preheated oven for 20 minutes. Cool for 10-15 minutes, and then slice into bars. Once completely cool, lift out of the pan. Store in an airtight container in the fridge.