We keep our hatchlings individually in their own shoebox-size sterilite container. We use moist papertowels as a substrate, with a hide and shallow water dish until they have their first poop.
I keep 1-2 hatchlings of the same size in either a shoebox size tub or 1/3 of a 20 gallon long enclosure, meaning their portion is 10"x12". When newly hatched, I have only a hide in the enclosure and mist it 2-3 times daily. After their first poo I add water dish, food bowl with a few mealworms and calcium dish. I use tile substrate for the tanks and no substrate for the tubs in the rack. I make small humid hides out of plastic baby food containers for the tanks. I don't use humid hides in the tubs because the enclosed nature of the rack raises humidity. I keep them in these enclosures until I sell them.