Cut the ribs into pieces that will fit standing up in the slow cooker. Lay the ribs on a cutting board and sprinkle generously with salt and pepper. In a small bowl, mix the Chinese five- spice and garlic powder together, then massage onto the meat to coat the ribs. Toss the jalapeño rings into the bottom of the slow cooker, and add the rice vinegar, coconut aminos, and tomato paste. Stir until the tomato paste is combined with the other liquids. Add the ribs, standing up so they’re not lying in the liquid – or use a roasting rack inside the cooker so the ribs are not lying on the bottom – cover, and cook 6 hours on high or 8-10 hours on low. When the ribs are fall-apart tender, remove them from the cooker. Pour the liquid into a heat-proof container and refrigerate until the fat separates from the juices. Remove the fat and bring the remaining liquid to a boil, then simmer for a few minutes. Use as a dipping/drizzle sauce for the meat. Want ‘em crispy? Throw the ribs in a 400F oven for 10 minutes while you boil the sauce.