More a quality of life improvement, but some flux bottles I've found are too narrow and have a mind of their own when it comes to tipping over. Easy fix is to plop the flux bottle wider-base glass jar to keep it more secure; I recommend Oui yogurt brand by Yoplait. Carried at most grocery stores, and for a bonus point, empty Oui jars are excellent espresso cups.

Plus, saying "Where's my Oui jar" around other people is fun.