There must be many ways to provide a root anchor.
I am starting my seedlings in 1-1/2" rock wool cubes, and will
move them in to a large block of rock wool then bury under clay pellets.
In Ron's system, you could start seedlings in the small cubes and then
transfer to a net basket (is that the right name) that are placed in the
expanded clay. This makes transplanting the seedlings with minimum shock very easy.