- Preheat the oven to 180C. Grease and line a 20cm square tin with baking parchment.
- Put the peanut butter, sugar, honey and oil in a saucepan and heat over a low-medium heat for a few minutes until the mixture is combined and the sugar has dissolved. Remove from the heat and stir in the raisins and oats.
- Transfer the mixture to the tin and use the back of a spatula to press down and push the flapjack mixture into all four corners.
- Bake in the hot oven for 20-25 minutes until golden brown. Remove from the oven and use a sharp knife to cut into 12 pieces while still warm. Allow to cool in the tin for 10 minutes before carefully transferring to a cooling rack to cool completely.