I forgot to tell you about the paste. You need a mortar. If you haven’t got one I guess you could smash the pepper in a paper bag (not plastic??) and crush the garlic in some other way.
Anyway, if you do have a mortar, take a little handful of peppercorns (30-40), crush them thoroughly, then add the garlic and crush it equally fine, then the sage in the same way (or at least mix it in…).