In a bowl, mix BBQ sauce and orange marmalade until well combined.

Place the boneless pork shoulder at the bottom of the slow cooker.

Chop the large onion into small pieces.

Cover the pork shoulder with the chopped onions.

Pour the BBQ sauce and marmalade mixture over the pork and onions.

Close the lid of the slow cooker.

Cook on low heat for 8-10 hours, or on high heat for 4-6 hours.

Remove the cooked pork from the slow cooker.

Cut the pork into smaller pieces.

Shred the pork with a fork until it is finely shredded.

Return the shredded pork to the slow cooker.

Stir the shredded pork in the sauce until it's evenly coated.

Serve the pulled pork on lightly toasted buns.

Consider adding mayonnaise to the buns to prevent sogginess.