Slow cook pork shoulder without it falling apart
It can be done, but requires a bit more time.  The trick is to cook it, then cool it, then heat it back up again:


Cook the pork shoulder
Drain the liquid, being careful not to poke at the meat too much
Remove the crock from cooker, and let it cook down
Place the crock in the fridge, and let chill overnight


The next day you can slice the meat, then pour the juices back over it to warm it back up.  (or reduce the juices to make a sauce)