1. Preheat the oven to 350°. Butter an 8-inch square baking pan and line the bottom and sides with parchment paper. Spread the chopped pecans in a pie plate and toast for about 5 minutes, until lightly browned and fragrant. Let cool.
2. In a large bowl, whisk the flour with the rolled oats, granulated sugar, brown sugar, salt, baking soda and pecans. Using a wooden spoon, stir in the melted butter until the oat mixture is thoroughly combined.
3. Press two-thirds of the oat mixture in an even layer on the bottom of the prepared baking pan and top with the raspberry preserves. Sprinkle the preserves with the remaining oat mixture.
4. Bake the bars for about 45 minutes, rotating the pan halfway through baking, until the top is golden brown. Transfer the pan to a wire rack and let the granola bars cool completely, about 3 hours. Cut into squares and serve.