Cut the onion into wedges and place at the bottom of the slow cooker. Add the roast, seasoning liberally with the salt and pepper. Pour over the entire can of chipotles, Worcestershire sauce and orange juice.
Cook on high for 4 hours or low or about 8 hours until the pork is pull apart tender. If desired, after cooling move the entire bowl to the fridge and cool overnight. Remove the excess fat, warm through and shred to enjoy.
Notes
As an optional bonus, save the excess fast to fry up portions of the shredded meat to enjoy as quick carnitas tacos!