Combine the beef stock, soy sauce, rice, sugar, garlic, pears and ginger in the bowl of a slow cooker. Stir to combine. Add the short ribs and turn to coat. Cover with a lid and cook on low for 3 hours, and then flip the meat and cook until very tender and falling away from the bone, another 3 to 4 hours.
Transfer the short ribs to a plate and cover with foil to keep warm. Use a large metal spoon to skim off as much fat as you can from the cooking liquid and remove the ginger. Blend the liquid in the slow cooker until smooth using an immersion blender or regular blender. Stir in the vinegar and sesame oil and season with salt and pepper.
Remove the bones from the short ribs and shred the meat into bite-size pieces, discarding the gristle. Return the shredded short ribs to the sauce and toss to coat. Cover with a lid and keep warm on the low setting.
Fill a large Dutch oven with 2 inches of canola oil and heat to 375 degrees F.
Cut the wonton skins in half diagonally to create two triangles. Fry the wonton skins in batches until golden brown and crispy, flipping occasionally, 2 to 3 minutes. Transfer to a paper towel-lined baking sheet with a slotted spoon to absorb any excess oil. Sprinkle liberally with salt.
To assemble, spread the fried wonton skins onto a large platter. Spoon the short ribs all over the wontons using a slotted spoon, and then top with 1 cup of chopped kimchi. Garnish with the sliced scallions and serve any leftover sauce on the side with the remaining chopped kimchi.