Preheat the oven to 350 degrees F (175 degrees C). Grease an 8x8-inch square pan; line with greased foil.

Combine flour, oats, brown sugar, baking soda, and salt in a large bowl. Rub in butter using your hands or a pastry blender to form a crumbly mixture.

Press 2 cups oat mixture into the bottom of the prepared pan. Spread jam to within 1/4 inch of the edge. Sprinkle remaining crumb mixture on top; press down lightly into jam.

Bake in the preheated oven until lightly browned, 35 to 40 minutes. Allow to cool before cutting into bars.