Incubation substrate, what do you use and why?

[Ally.]

After 2 weeks the eggs will be flat on the bottom, before that I use plastic clips that hold them from rolling.

If the perlite/vermiculite has too much water then yes the egg crate will sink.
I use two pieces of egg crate per tub and that has eliminated the sinking of the egg crate.
Some people cut 4 pieces of 1/2" pvc pipe and place the egg crate on those.

Awesome, thank you!