You can leave the sand and pour directly on it.
Wet the sand down good prior to the pour.
If you do not wet the sand as you dump loads of concrete dry sand will be picked up more not a good thing.
I find welded wire mesh the best for thinner slabs, we used to mix bales of zonolite in our pool bottom and side wall mix I don’t remember the ratio but it worked well with welded wire, we installed a bunch of pools with liners this way years ago back then it was not considered permanent but I believe they changed the law if you still have the above ground temporary part the bottom being concrete won’t change the tax status.
But you can pour over wet sand, and you might have better luck with welded wire reenforcement over rebar.