Line an 8×8-inch pan with parchment, leaving overhang for easy lifting. A loaf pan works for thicker bars.
In a dry skillet over medium heat, lightly toast the oats and nuts for 3–4 minutes until fragrant. Stir frequently. Let cool slightly. FYI, this step upgrades the flavor fast.
In a small saucepan on low heat, warm the nut butter, sweetener, and coconut oil until melted and smooth. Stir in vanilla and salt. Do not boil—just melt.
In a large bowl, add oats, nuts, seeds, and any dry add-ins (except chocolate chips if the mixture is hot). Pour the warm mixture over and stir until everything is evenly coated and glossy.
If adding chocolate chips, let the mixture cool a couple minutes so they don't melt completely. Then fold them in gently.
Transfer to the lined pan. Press very firmly with a spatula or the bottom of a measuring cup. The tighter you press, the better the bars hold.
Refrigerate for 1–2 hours, or freeze for 25–30 minutes, until firm.
Lift out using the parchment. Cut into 10–12 bars with a sharp knife. For clean edges, warm the knife under hot water and wipe between cuts.
Eat immediately or store using the tips below. Try not to eat half the pan. Or do. Your call.