Whisk until there are no lumps. It should make a paste.
Slowly add spoonfuls of ham broth, whisking continually as you do.
Whisk, whisk whisk! It should be thickening. Keep low heat. If it's not thickening, stop adding broth for a couple minutes, but keep stirring as it thickens.
Since ham is naturally salty, make sure to taste the gravy before adding any to taste.
Serve in a pretty bowl with a ladle for easy serving.