Starting to use Iceberg again, question about faux-roots

I've just started using Iceberg again after a while and was intending to base .pkg builds off of pkgGen output. A few times (eg., https://www.afp548.com/forum/viewtopic.php?showtopic=24079) I've seen people mention using similar workflows. Those that are (or have), are you manually adding the contents of the pkgGen generated faux-root directory or is there a way to just have Iceberg generate a project from that directory tree? I feel like I'm missing something...