Preheat the oven to 180C/350F. Line an 8 x 8-inch pan with parchment paper and set aside.
In a large mixing bowl, add the oats and brown sugar and mix until combined. Add the coconut oil and golden syrup and mix until fully incorporated.
Transfer the flapjack mixture into the lined pan and press down until smooth on top. Place the flapjacks in the oven and bake for 17-20 minutes, until the edges are beginning to go golden brown.
Remove the flapjacks from the oven and let them cool in the pan for 10 minutes, before transferring to a wire rack to cool completely. Once cool, slice into bars.
TO STORE: Flapjacks will keep at room temperature, covered, for up to 2 weeks. TO FREEZE: Place leftover flapjacks in a ziplock bag and store them in the freezer for up to 6 months. TO THAW: Allow flapjacks to thaw to room temperature before enjoying them.