Prepare Your Pan: Line an 8x8-inch baking dish with parchment paper, leaving extra hanging over the sides for easy removal.
Mix Dry Ingredients: In a large bowl, combine the 2 cups of oats and your 1/2 cup of mix-ins, such as chocolate chips, dried fruits, or nuts.
Heat Wet Ingredients: In a small saucepan over low heat, melt the 1/2 cup of nut butter and 1/3 cup of honey (or maple syrup/agave) together, stirring until smooth and fully combined. Stir in the teaspoon of vanilla extract if using, and a pinch of salt.
Combine Wet and Dry Ingredients: Pour the melted nut butter mixture over the oat mixture and stir well to combine. Make sure all the oats are coated.
Press into the Pan: Transfer the mixture to your prepared baking dish. Press it down firmly with the back of a spoon or spatula to ensure it's packed tightly and evenly.
Chill: Place the pan in the refrigerator and let it chill for at least 2 hours, or until the bars are firm enough to cut.
Slice and Serve: Once set, lift the bars out using the parchment paper and cut into 10-12 bars. Enjoy immediately or store for later!