I've always recommend leaving the soiled litter box outside, or spread some of the contents around your yard. (If you have one.) I always did this whenever I moved. Never read it, just my intuition and common sense. But I never considered that this could be dangerous for my cat's health. Check out this Quora answer:
If you leave the litterbox outside, you will need to replace or sterilize it before your cat can use it indoors again. (FELV risk definitely, maybe other things as well). I’d just buy a new one and keep it indoors so the second she is back, she has a box and you don’t have to worry about disease and the box outside that may have been exposed. Finding A Lost Newly Adopted/Indoor-Only Cat
https://www.thesprucepets.com/how-to...st-cats-552309