Spray the inside bowl of a slow cooker with non-stick cooking spray.
Place frozen meatballs in the slow cooker first.
Pour the grape jelly and chili sauce over the meatballs. Give it a stir to make sure the meatballs are all coated.
Cook on high for 2 hours, or low for 4 hours.
Once the meatballs are done cooking, add in the cornstarch slurry. Stir and continue to cook until sauce starts to thicken. This will take about 3 minutes. Change the slow cooker setting to the warm setting until you are ready to serve them.
Serve as an appetizer with toothpicks, or as a meal with rice if you desire.