Cut the slab into smaller sections so the ribs fit easily into your pot.
Add the chicken stock, onion, garlic, salt, pepper, smoked paprika, garlic powder, and onion powder to a large stock pot.
Place the ribs into the pot and bring everything to a gentle simmer over medium heat.
Cover and simmer for about 1 hour 45 minutes to 2 hours, or until the ribs are very tender and almost falling apart.
Preheat the oven to 400°F.
Line a baking tray with parchment paper and carefully transfer the ribs onto the tray.
Brush the ribs generously with homemade BBQ sauce on all sides.
Bake uncovered for 20-30 minutes, brushing with more sauce halfway through, until the ribs are sticky, caramelized, and slightly charred around the edges.
Let the ribs rest for a few minutes before serving.