Guide to Unix/BSD/OpenBSD/Customize Installation
You may want to customize your installation if:
- you want to install a new set of packages during the OpenBSD installation.
- if you want to report an installation problem.
- If you want to change the default configuration files.
Inside the iso 
Mount the iso and cd into it. See the Guide to Unix Explanation section on how to mount an iso file. Then the <your OpenBSD release>, and then <your processor> directory.
cd /<where the mounted iso is located>/<your OpenBSD release>/<your processor>
For me it is:
(My auto-mount system gives the files that it mounts long names).
For OpenBSD 4.4 i386 it is:
4.4 i386 BASE44.tgz boot.catalog bsd bsd.mp bsd.rd cdboot cdbr comp44.tgz etc44.tgz game44.tgz man44.tgz misc44.tgz xbase44.tgz xetc44.tgz xfont44.tgz xserv44.tgz TRANS.TBL TRANS.TBL etc. TRANS.TBL boot.conf TRANS.TBL
|File or Exec||Description|
|"RAM Disk" kernel.|
|The OpenBSD kernel.|
|Multi-processor (SMP) kernel.|
|Contains the base OpenBSD system.|
|Contains all the files in /etc.|
|Contains the compiler and its tools, headers and libraries.|
|Contains the man pages.|
|Contains misc info, setup documentation.|
|Contains games for OpenBSD.|
|Contains the base files for X11.|
|Contains the /etc/X11 and /etc/fonts configuration files.|
|Contains X11's font server and fonts.|
|Contains X11's X servers.|
|Contains manpages, locale settings, includes, and others for X.|
Take the packages out of the iso and edit them as described below. Then take all of the files and make a new iso.
Install additional packages 
Cd into the iso as directed before. Now change the file permissions. If you want another package installed as an option. Take the package and rename it (do not put a period):
site<your version>-<the package name>.tgz
For abiword on OpenBSD 4.4, it is:
You will also have to find its dependencies and include them as well.
Change configuration files 
Untar etc44.tgz. You will find all of the default configuration files in etc. inside of the package. Edit them and retar them.