Start by preheating your oven to 350°F and greasing your baking sheet with a light coating of butter or cooking spray. While the oven heats, plump your raisins by covering them with warm water and letting them sit for 5 minutes, then drain them thoroughly and set aside. Measure out all your dry ingredients (gluten-free flour blend, baking soda, cinnamon, and salt) into one bowl so they're ready to go. This prep work ensures everything is ready when you need it and prevents any rushed moments during mixing.

In a large mixing bowl, combine the softened butter, white sugar, and packed brown sugar. Beat them together for 2-3 minutes until the mixture becomes light, fluffy, and pale in color. This creaming process is crucial because it incorporates air into the dough, which helps the cookies rise slightly and achieve a better texture. I like to use an electric mixer on medium speed for this step to ensure even incorporation, but vigorous hand-mixing works too.

Add the room-temperature egg and vanilla extract to your creamed butter and sugar mixture. Stir or beat until fully incorporated, about 1 minute, until the mixture looks smooth and well combined. Using room-temperature eggs ensures they blend seamlessly into the butter without causing the mixture to break or separate.

Add the dry ingredient mixture from Step 1 to your wet mixture from Step 3. Using a spatula or wooden spoon, fold gently until you just barely see no white streaks of flour remaining. Don't overmix at this stage—overworking gluten-free dough can make cookies tough and dense. Stop folding as soon as the dry ingredients are incorporated.

Fold the old-fashioned oats and drained raisins into the dough using the same gentle folding technique. Mix just until the oats and raisins are evenly distributed throughout the dough. I find that folding rather than stirring helps maintain a tender cookie texture, especially important with gluten-free baking where we don't have gluten's natural elasticity to help the cookies hold together.

Using a cookie scoop or two teaspoons, drop rounded portions of dough onto your prepared baking sheet, spacing them about 2 inches apart to allow for slight spreading. Bake for 9-11 minutes, until the edges are light golden brown but the centers still look slightly underbaked—they'll continue to cook as they cool. The cookies should look just set but still have a touch of softness in the middle.

Remove the baking sheet from the oven and let the cookies rest on the hot sheet for 1-2 minutes—this allows them to firm up slightly so they won't fall apart when moved. After resting, carefully transfer the cookies to a wire rack to cool completely. This short resting period on the baking sheet is the key to getting cookies that hold their shape beautifully.