Prepare your ribs by cutting each rack in half.
Place the ribs in your 6-quart slow cooker with the bone side down.
Add sliced onions and minced garlic on top of the ribs.
Sprinkle with salt and black pepper.
Place the lid on the slow cooker.
Set the slow cooker to low and cook for 8 hours.
Ensure you don't lift the lid during cooking to keep the heat consistent.
Once done, transfer the ribs onto a baking sheet and cover them with foil to keep them warm.
Strain the cooking juices from the slow cooker into a large skillet.
Add honey, soy sauce, and vinegar to the skillet, and bring the mixture to a boil over medium-high heat.
Mix cornstarch with cold water and stir this into the skillet to thicken the sauce.
Pour the sauce over the ribs and let them rest covered.
For the slaw, combine shredded cabbage and grated carrot in a large bowl.
In another bowl, mix together mayonnaise, apple cider vinegar, sugar, celery seed, and salt.
Pour the dressing over the cabbage and carrot mixture and toss well.