In the fridge, you can keep the leftover cake in an airtight container for about 3-5 days. Although, you should ideally finish it as soon as possible if you want to taste the best quality cake! If you want to freeze the individual slices, you should start by wrapping each piece in parchment paper or cling wrap, then placing it into a freezer-safe baggy. To thaw the cake slices, bring them to room temperature if they are already frosted. You can set the cake in the microwave for 30 seconds or so if it's not frosted. Also! You can freeze the unfrosted cake a day before serving and then make and add the frosting when ready to serve. I’ve done this before!