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 together well. Next, work in butter with a fork until the mixture is crumbly.
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 30 minutes. Slice into squares and enjoy!