All of these questions are very dependenton someones tradition, what the intention is and what type of jar it is.
Jar spells are very variedand cross over traditions making their use and disposal very variable.
There are many types. What is it that you want to accomplish?
you could dispose of them in many ways just depends on what your doing, ways to dispose are leaving them at crossroads, burying them at graveyards, sometimes people bury it in their backyard, it really just depends on what ur doing