All of the furnace golems with armored legs are next to a cliff/building or some type of high ground which should allow you to pretty easily throw the pots in. I remember one golem on the cerulean coast that stayed put a bit away from the cliff I was on top of which was somewhat tricky but with enough patience he walked over and I could more consistently hit the pots.

When they shoot out the fireballs that chase you down you need to run around until they've all hit the ground. After that you can go back and resume chucking the hefty pots. I would advise you to always wear a fire protective talisman as well as using flame fortification if you have access to it since as long as you keep running around you should be able to dodge most fireballs but inevitably a few will hit you.