Prepare filling first. Combine dates, hot water, maple syrup and salt in a saucepan. Cook over medium-low heat until the dates are softened, and the water is absorbed. Stir in vanilla and set aside to cool.
Preheat oven to 350º (177ºC) and prepare parchment-lined 8-inch square cake pan.
In a medium-sized bowl, whisk together flour and baking soda. Add oats and brown sugar and mix well. Next, work in butter with a pastry blender or fork until the mixture is crumbly and the butter is well distributed throughout.
Spread half the oat mixture into the bottom of the prepared baking pan, pressing it down with the back of a wooden spoon to form a base. Cover with cooled date filling. Next, sprinkle remaining oat mixture across the top.
Bake for 20-25 minutes until lightly browned. Remove from oven, place pan on wire cooling rack and let cool for at least 30 minutes. (For a cleaner cut, chill in the refrigerator for up to an hour once cooled). Slice into squares and enjoy!