It is very easy to reheat the borek and you can reheat them straight out of the freezer without defrosting. Wrap them in tinfoil and then place them in a preheated oven (180° C) for about 10 minutes, or until they are piping hot in the middle. Give extra 5 minutes for frozen boreks. Alternatively, you can reheat them in a microwave for a couple of minutes but they would lose their crispness.