Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang for easy removal.

In a large bowl, combine the rolled oats, flour, brown sugar, baking soda, and salt. Mix well.

Pour the melted butter into the dry ingredients and mix until just combined to form a crumble mixture. Reserve about 1 cup of this mixture for the topping.

Press the remaining oat mixture firmly and evenly into the bottom of the prepared baking pan to form the base layer.

Prepare the filling: In a small saucepan, combine the chopped dried apricots, water, and lemon juice. Bring to a gentle simmer over medium heat and cook for 5-7 minutes until the apricots have softened and the liquid has thickened slightly. Remove from heat.

Spread the warm apricot filling evenly over the pressed base layer.

Sprinkle the reserved 1 cup of oat mixture evenly over the apricot filling. Gently pat down so it adheres slightly.

Bake for 25 to 30 minutes, or until the topping is golden brown and the edges are slightly set.

Let the slice cool completely in the pan on a wire rack before lifting out using the parchment overhang and cutting into 12 squares. Cooling fully is crucial for clean slicing.