slackbuilds.org

I've found this website : www.slackbuilds.org that provides packages for Slackware, to be compiled with the SlackBuild scripts. Usage of the slackbuild script can be found here. The resulting Slackware official package is then to be installed with installpkg command. Typically, the resulting package will be in /tmp.

Installation of openoffice.org

First download the slackbuild script here.
Untar it.
Download the source from here.
Copy the source the the slackbuild directory:
cp OOo_2.3.0_LinuxIntel_install_en-US.tar.gz openoffice.org
Make the script executable:
chmod +x openoffice.org.SlackBuild
./openoffice.org.SlackBuild
When done creating the package, install it with installpkg:
cd /tmp
installpkg openoffice.org-2.3.0_en_US-i586-1_SBo.tgz