Preheat your oven to 180°C (350°F) and line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal.
In a mixing bowl, combine the oats, brown sugar, cinnamon, and salt. Stir well until evenly mixed, creating a fragrant, speckled dry mixture.
In a small saucepan, melt the butter over low heat until just bubbling and smooth. Remove from heat.
Pour the melted butter over the dry mixture. Use a spatula to fold and stir until all oats are coated and the mixture is crumbly but starts to stick together.
Transfer the mixture to your prepared baking pan and press down firmly with the back of a spatula or your fingers, creating an even, compact layer. This helps the bars hold together when baked.
Bake in the preheated oven for 20–25 minutes, until the top is golden brown and fragrant with toasted oats and cinnamon. Keep an eye on it around 20 minutes to prevent over-browning.
Remove the pan from the oven and let it cool in the pan for about 10 minutes. The mixture will firm up as it cools and become easier to cut.
Use the parchment overhang to lift the cooled block out of the pan. Place it on a wire rack and let it cool completely before slicing into squares or rectangles.
Once cooled, cut into 12 bars with a sharp knife, using a gentle sawing motion for clean edges. Serve immediately or store in an airtight container for later.
