Heat oven to 200C/180C fan/gas 6 and line a 20 x 20cm baking tin with parchment. Melt the butter, sugar, honey and a pinch of salt in a pan. Once the mixture is bubbling and combined, stir in the oats.
Tip the oat mixture into the lined baking tin and press down with the back of a spoon. Scatter over the raspberries, then lightly press them into the oat mixture. Bake for 25-30 mins until golden brown. Leave to cool, then cut into 9 or 12 flapjacks.