I buy the zerust tabs from gander and just cut them up into various sizes and toss in the the boxes. Simple and cheap, especially if you already have boxes. No need to buy flambeau boxes.
http://www.gandermountain.com/modperl/product/details.cgi?pdesc=Flambeau-Zerust-6004R-Tuff-Tainer-Divider-Packs-12-Pk-6012ZP&i=761395