You will also need a 20cm x 30cm (8in x 12in) cake tin, greased
Put the lactose free butter, sugar, cinnamon and maple in a saucepan and heat, stirring occasionally, until the butter has melted and the sugar has dissolved.
Add the oats and gluten free flour and mix well. Transfer the oat mixture to the prepared cake tin and spread to about 2cm (¾in) thick.
Smooth the surface with the back of a spoon. Bake in a preheated oven at 180C/350F/Gas 4 for 15-20 minutes, until lightly golden around the edges, but still slightly soft in the middle. Let cool in the tin, then turn out and cut into squares.