I didn't specifically intent to freeze-dry them. I only meant to dry them (in my multi-level air-circulating dryer). But for extra proof against spoilage, I store the dried apples in zip-lock bags in my big freezer. And somehow that ends up sucking the last of the moisture out of them. They're solidly dried when I put them in, but when I get them out, they're actually crisp.

The thing that makes this all possible is I have one of those crank apple peeler-corer-slicer devices. So when it's apple season, once a day I bag the last day's dried slices, then process enough apples to fill the drier again. The whole process takes less than half an hour, but it requires me to process every single day from start of harvest until they're all done because the processing rate is limited by the drier size.