Turn the heat off on the crock pot. Put the lid on and wait.
After a while - an hour or so, stir it some more. It should have softened some by now, but will likely still be very chunky and gooey. Put the lid back on and wait some more.
I often plan my liquid soap batches so that at this point I can just put the lid on and go to bed, leaving it to sit overnight and dissolve. But if you want to take a more active role, just keep waiting and stirring, waiting and stirring. The potato masher will help to break up some of the larger chunks of paste, but nothing will help more than just waiting.
For more information on diluting your soap, and a handy reference table, I've created a Liquid Soap Dilution Table