In a large mixing bowl, combine the rolled oats, all-purpose flour, baking soda, ground cinnamon, and salt. Stir well to evenly distribute the dry ingredients.
Add the packed light brown sugar and granulated sugar to the bowl and mix thoroughly.
Gently fold in the raisins, ensuring they are evenly dispersed throughout the mixture.
Carefully layer the mixture into a clean 1-quart (4-cup) glass jar, pressing down lightly to compact the ingredients without crushing the oats or raisins.
Seal the jar tightly with a lid and attach a label or tag with the following baking instructions:
Baking Instructions:
1. Preheat oven to 350°F (175°C).
2. In a medium bowl, beat together 1/2 cup (1 stick) softened unsalted butter, 1 large egg, and 1 teaspoon vanilla extract until creamy.
3. Add the contents of the jar to the wet ingredients and stir until just combined.
4. Drop rounded tablespoons of dough onto a parchment-lined baking sheet, spacing them about 2 inches apart.
5. Bake for 10-12 minutes, or until the edges are golden brown.
6. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.