Measure the oil, maple syrup, peanut butter and vanilla into a small saucepan and heat gently, stirring with a whisk until the mixture just starts to bubble and the peanut butter is completely soft.
Put the oats, nuts and seeds in a large mixing bowl and pour over the peanut and maple mixture, then give everything a really good stir. Divide the oat mixture between two large baking trays and place in the hot oven for 15 minutes. Remove the trays and stir well, before returning the trays to the oven but swapping them round so that the tray that was on the bottom is now on the top and vice versa. Cook for a further 15 minutes before removing the trays and scattering over the raisins (add them any sooner and they will burn). Stir and return to the oven for a final 10 minutes.
Allow the trays to cool slightly before decanting into a jar or airtight container. Eat within a month.