One way to preserve your gingerbread house is to let it air dry, which can take several days or even weeks. You'll need to place it in a cool, dry place, away from direct sunlight and moisture. Just be patient and let it dry out slowly – it's worth the wait!
But, if you're not feeling patient, you can try using a food dehydrator to speed up the process. This will help to draw out the moisture from the gingerbread, leaving it dry and sturdy. Just be careful not to overdry it, or it'll become too brittle!