it depends on what the problem is to determine which kind of poultice to use.
Herbal poultices are easy to make:
just take a cup or two of the chosen herb and grind it up with water to make a paste,
apply to the area and hold it down with gauze or cheesecloth...
you can google different home remedies and different poultices as well
eta: there are some herbs that should NOT be used in poultices, google herbal remedies for whatever problem you have and they should tell you what not do to and what to do...I'm not an herbalist, so...