My starter pack came with a coir type brick that I had to soak & crumble to give them a medium to establish (&hide) in. On that basis, a layer of soil or compost on the bottom would be a good start.
BTW, with all this talk of identity fraud, I have always shredded my official stuff and then added the shavings to my wormery. I know there have been concerns here about the inks being toxic, but my boys have never bothered & as long as it's there with plenty organic stuff, I'll continue with it. It also helps regulate the moisture content when it gets sludgy.
