Remove stems from figs and discard. Coarsely chop figs and place in jam pot. Add sugar and salt, stir to combine. Remove peel from lemon using a microplane grater. Add zest to pot. Add liqueur. Stir and let sit for 1 hour. Stir occasionally.
Cook over medium heat until figs come to a boil. Reduce heat and simmer, stirring occasionally, until jam thickens (35-45 minutes). When stirring, use the back of your spoon to mash the figs into small pieces. You will know it is ready when you can place a spoonful of jam on a cold plate (refrigerate a plate for 1 hour to prep) and jam sticks (does not run).
Ladle hot jam into hot jars leaving 1/4 inch headspace. Wipe rim. Center lid on jar. Apply band until fit is fingertip tight. Process in a boiling water canner for 10 minutes, adjusting for altitude. Remove jars and cool. Check lids for seal after 24 hours. Lid should not flex up and down when center is pressed.
(Note, if you are new to canning/preserving, check out the resource guide at Ball)