Gently warm the olive oil in a saucepan. Add the chilli flakes and whole chillies to the oil and heat for 3-4 minutes. Remove from the heat and leave the oil to cool slightly.
When the oil has cooled, carefully strain it into a sterilised, sealable glass bottle using a funnel. Add dried chillies from the pan and seal the bottle.
Keep the bottle in the refrigerator and use within one week.
You can use more or less chillies, depending on the heat you require. To sterilise bottles, wash the bottles in very hot water or put them through the hot cycle of a dishwasher. Place the bottles onto a baking tray and slide into an oven set to 160C/325F/Gas 3 for 10-15 minutes. Keep them warm until filled with the oil.