The procedures for configuring and maintaining a custom LOCAL package are similar to those outlined in §3.5 for installing and maintaining layered software, since a custom LOCAL will in fact be a layered software product, possibly even something one might want to export to another site (although custom LOCALs may contain non-portable or site specific software).
To make a custom local you make a copy of the "template local" package (iraf$local) somewhere outside the IRAF directory tree, change the name to whatever you wish to call the new layered package, and install it as outlined in §3.5. The purpose of the template local is to provide the framework necessary for a external package; a couple of simple tasks are provided in the template local to serve as examples. Once you have configured a local copy of the template local and gotten it to compile and link, it should be a simple matter to add new tasks to the existing framework.