Take a flat utensil such as a fork or a knife and stick it between the top bun and the patty on the frozen slider. Gently separate the bread, so the meat is exposed, and place the bottom half inside the air fryer.This method will allow the meat to cook while not burning the top bun.
Remove the basket and put the top bun in the fryer next to the bottom half. Please do not put it on top, as this will stop the heating process for the meat.
Air fry for about 5–6 minutes at 375 °F or until the meat is adequately warmed up.
Air fry for another 2–3 minutes so the bun is crispy, the cheese is melted, and the meat is hot.
Let them sit for another few minutes so that they can cool. Remove the burgers from the air fryer and reassemble.
Afterward, enjoy your fully cooked White Castle sliders with some ketchup, mustard, or as-is.