there is always a couple of ways to do things. for the google gadgets for you desktop, it is its own seperate application. while for windows and mac, they have packaged it all together.while for linux there has been a seperate, not so publicized project for support.
so two ways of going about this for slackware, Build It or repackage it. the SlackBuild in my pub/src/ is a perfectly viable solution if you have all the build dependencies. Otherwise, just like my last post you can get their RPMS and use my repackaging script, to include all their installation scripts.