Place pork spare ribs in slow cooker insert. Combine all sauce ingredients in a small bowl.
In a small saucepan, heat vegetable oil. Saute garlic for 1 minute. Pour in sauce and allow it to come to a boil. Reduce heat, cover, and let it cook until thick and bubbly for about 3 minutes. Turn off heat.
Pour sauce over pork spare ribs in the slow cooker insert. Cover and cook on high for 6 hours.
To serve, transfer cooked spare ribs onto a platter. Skim off as much fat as possible from the remaining sauce. Strain into a small saucepan. Add corn starch mixture and boil until thick and bubbly, about 2 to 3 minutes. Pour over spare ribs.