Are you planning on dividing sterilite/tupperware tubs? Obviously clay would help to fit into the grooves and wells formed in a tub, but you have to take into account how it fits when a lid/shelf is on top of the tub as well. Clay would be messy, difficult to clean, and heavy. If you have one giant divided tub, where they all same the same lid/shelf that functions as a lid, how do you intend on moving or interacting with one snake, while also monitoring that the others are not stressed or escaping, or getting their head trapped when you close the tub?

Seems easier just to make a shelf that will function as a cubby-space that fits both the hatchling tub height and the adult height of the tubs, so that you can just use individual tubs as babies, and move to bigger tubs as they outgrow them, without replacing the shelf itself.