Smashed potatoes are best served fresh and hot, that is when they are the crispiest. To store, place in an airtight container in the fridge for up to 3 days.
To reheat
Microwave: Place your leftover potatoes in a microwave-safe dish and heat on high power for 2-4 minutes, checking and flipping the potatoes halfway.
Air fryer: Place potatoes in the air fryer or in the oven at 180C/370F for 5-6 minutes or until warmed through to your liking.
Oven: Place the potatoes on a lined baking tray, and bake in a preheated oven at 190C/374F for 12-15 minutes until warmed through and crispy.
Find it online: https://allguiderecipes.info/air-fryer-smashed-potatoes/