Mix apricots and lemon juice in a large pot; add sugar. Slowly bring to a boil, stirring until sugar dissolves. Cook and stir until apricot mixture thickens, about 25 minutes. Remove from heat and skim foam if necessary.
Meanwhile, prepare jars, lids, and rings by cleaning and sterilizing in dishwasher or boiling water bath. Leave lids in simmering water until ready to seal jars.
Ladle hot jam into hot sterilized jars, leaving about 1/4 inch of space on top. Run a knife or a thin spatula around the insides of the jars after they have been filled to remove any air bubbles. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids and screw on rings.
Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil, then carefully lower the jars into the pot using a holder. Leave a 2-inch space between the jars. Pour in more boiling water if necessary until the water level is at least 1 inch above the tops of the jars. Bring the water to a full boil, cover the pot, and process for 15 minutes.
Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart, until cool. Once cool, press the top of each lid with a finger, ensuring that the seal is tight (lid does not move up or down at all). Store in a cool, dark area.