Prepare: Mix the spices and divide it in half. Slice the onion into 1/4 inch thick slices. Mix the honey, water, vinegar and remaining spice mixture together.
Rub half of the spice mixture into the meat.
Heat oil a skillet over medium-high heat. Once the skillet is hot, add the pork and sear it on all sides.
Place the onion slices into the bottom of the slow cooker and top them with the seared meat.
Combine honey, vinegar, water and remaining seasoning mixture; pour it over the meat. Add the red pepper flakes if using. Cover the slow cooker and cook on low heat for 6 hours. Shred with two forks, or cut it into pieces.