Preheat the oven to 160°C/320F and greaseproof a baking tin.
Place the flour, sugar, coconut and oats into a bowl and mix to combine, making a well in the center.
In a saucepan over medium low heat place the butter and golden syrup until combined and melted.
Mix together the boiling water and baking soda. Add to the melted butter and stir to combine.
Remove from the heat and pour into the oat mixture.
Stir through until the entire mixture is coated in the butter syrup sauce, ensuring there are no clumps of flour or oats at the bottom of the bowl.
Spoon the entire mixture into your tin, spreading evenly.
Bake for approximately 25 minutes or until completely golden on top, but still soft enough to feel your finger slightly sink into the bars when touched lightly.
Remove and set aside to cool.
Meanwhile, melt the chocolate in a double boiler until smooth.
Remove and pour in the cornflakes, stirring to coat fully. If you crush the cornflakes in this process, don’t worry, that’ll help ensure they are fully covered in the chocolate.
Spoon every last ounce of the chocolate onto the cooled bars and spread out with the back of a spoon, it might feel a bit stiff to move about, but will cover the top by continuing to stir with the back of your spoon.
Sprinkle sea salt over the top and place in the fridge to set for at least 30 minutes.
Allow to come to room temperature before removing, slicing and serving.