I broke my pot using a hammer and a slot screwdriver (big kind) and hit one side and it cracked down then I did the same on the opposite side and it cracked beautifully quite even. Just don't smash really really hard just enough to start the split.
Make sure there are no sharp exposed edges. Tapping the pots with a hammer will smooth the sharp edges down. Do your breaking in a cardboard box. Wear eye protection! And the screwdriver helps to make some interesting breaks.
Please be carefull if you are going to try using pot(s)