Preheat oven to 350 degrees F. Line an 8 by 8-inch baking dish with aluminum foil, leaving a 2-inch overhang of foil on two sides. Grease foil.
In a large mixing bowl, whisk together flour, baking soda and salt. Stir in oats and brown sugar, and use clean fingertips as needed to break up brown sugar clumps. Add butter, and using fingertips, work butter into mixture until evenly moistened.
Add 2 cups of the oat mixture to the prepared baking dish and press into an even layer. Spread raspberry jam into an even layer over oat layer, coming within 1/4-inch of all edges. Sprinkle top evenly with remaining oat mixture, then slightly press into jam layer.
Bake in preheated oven until golden brown, about 34 - 38 minutes. Remove from oven and allow to cool completely before cutting into squares. Store in an airtight container.
If you'd like, you could add in a little ground cinnamon or fresh lemon zest to the oat mixture.