I want to add the link tags to redirect my web-site to my OpenID provider. These tags should go in the head element. What's the best way to add them in Plone?

I understand that filling the head_slot is a way to do it, but that can only happen when you are adding a template to the page and that template is being rendered. In my case I'm not adding any template. Which template should I modify (that is not main_template.pt, which is my current solution, with it's huge drawbacks).