Preheat your oven to 180℃ (or 160℃ for fan ovens) then line an 8x8 tin with baking paper.
Melt the butter, sugar and honey together over low heat on the stove. Stir gently until the butter has melted and sugar has dissolved.
Remove from the heat and stir in the oats.
Press the mixture firmly into your tin and bake for around 20 minutes. The flapjacks should be golden at the edges and wobbly in the middle. They'll firm up as they cool.
Let your flapjacks cool in the tin for around 5 minutes then use a knife to gently score lines where you plan to cut them. This will help to prevent crumbling later.
Leave the flapjacks to cool completely (about 2-3 hours) then remove them from the tin. Cut into slices and enjoy!
Video
Notes
Store in an airtight container in the fridge for up to 1 week.