Hi Sarah, good to see another Aussie here

Sand is (as Ginger & Lee said) a no...

Soil on the other hand, (from experience) isn't the best, but can be all right as long as it is kept reasonably firm/moist, has been treated to ensure no parasites or other nasties are hiding inside it and mustn’t be chemically treated... still, I wouldn’t recommend dirt/soil..
I believe the best thing to use in your position would be paper towels, (preferably a brand with no odor/no chemicals). For me, paper towels work great for a temporary substrate, and although it makes it easy to clean, you might have to do it more often than not… doesn’t look too great… but it does the job… you feel me?

Try and find some coco husk that stuff is the bomb.

Goodluck