How to make apple crisps in the ovenOur apple crisps take a total of three hours in the oven, so plan to make them when you have a morning or afternoon at home. Healthy apple crisps recipeStep 1Heat the oven to 120C/fan 100C/gas ½. Cover a large baking sheet or tray with a sheet of baking parchment. Step 2Using a sharp knife or mandolin cut your apple into thin slices, about 2 mm is ideal. Step 4After 2 hours is up turn off the oven completely and leave the apple slices in there for at least another hour for further drying.