Well, Vermouth is really just aromatized and fortified wine.
Aromatized just means that the wine has a bunch of roots, flowers, and other plant parts soaking in it for extra flavour and aroma.
Fortified means that extra booze was added to it too.
So what I do is I put stuff into wine and then I add booze to it.
Well, it's more complicated than that because I also add stuff to the booze too, and the stuff that I add is a pretty special blend of a few different types of Wormwood, Yarrow Flowers, Clover, Lavender, Chamomile, Gentian, Linden, Lemon Balm, Hibiscus, Sage, Rosemary and the list goes on.
All in all, there are 26 ingredients for the red/sweet vermouth and 12 for the white/dry vermouth. Each ingredient is extracted for a specific time to get the right balance of bitter, sweet, fruity, herbal, floral, and spice notes.