In a large mixing bowl, thoroughly combine all dry ingredients, including certified gluten-free rolled oats, chopped nuts, seeds, dried fruits, and any optional mix-ins or spices.
In a separate saucepan, gently heat your chosen wet ingredients (binders like nut butter, honey, maple syrup, or brown rice syrup) until just melted and well combined. Do not boil.
Pour the warm wet mixture over the dry ingredients in the large mixing bowl. Stir vigorously and thoroughly until all dry ingredients are evenly coated and sticky. Ensure no dry spots remain.
Line an 8×8 or 9×13 inch baking pan (depending on recipe yield) with parchment paper, leaving an overhang on the sides for easy removal. Transfer the granola bar mixture to the prepared pan. Using a sturdy spatula or the bottom of another flat object, press the mixture down incredibly firmly and evenly across the entire surface of the pan. The firmer you press, the better the bars will hold their shape.
If baking for a crispier texture, bake according to your specific recipe’s instructions, typically at a lower temperature (e.g., 300-325°F or 150-160°C) for 20-30 minutes, or until edges are golden brown. For chewy bars, baking time will be shorter or you might skip baking entirely for no-bake bars.
Whether baked or no-bake, allow your bars to cool completely to room temperature in the pan. Once cool, transfer the pan to the refrigerator and chill for at least 2-4 hours, or ideally overnight. This chilling time is crucial for the bars to set firmly and allow for clean cutting.
Once thoroughly chilled and firm, lift the granola block out of the pan using the parchment paper overhang. Place it on a cutting board and cut into individual bars of your desired size. Store the bars in an airtight container at room temperature for up to one week, or in the refrigerator for up to two weeks. For longer storage, wrap individual bars and freeze for up to three months.
