Make the sauce base: In a bowl, whisk together sweet chili sauce, ketchup, soy sauce, rice vinegar, honey, sriracha (if using), garlic, and ginger until smooth.
Load the slow cooker: Add frozen meatballs to a 5- to 6-quart crockpot. Pour the sauce over the top and stir to coat.
Cook low and slow: Cover and cook on Low for 4 to 5 hours, or on High for 2 to 3 hours, until the meatballs heat through and the sauce bubbles gently.
Thicken if you like: If you want a stickier glaze, whisk the cornstarch with cold water, stir it into the sauce, and cook for 10 to 15 minutes more until glossy and thick.
Finish and serve: Taste and adjust seasoning—add a squeeze of lime for brightness or a drizzle of honey for sweetness. Garnish with green onions and sesame seeds. Serve hot.
Don’t overfill: Keep the crockpot under three-quarters full so the sauce heats evenly and thickens.
Stir occasionally: Give everything a gentle stir halfway through to coat every meatball.
Hold on warm: Switch to Warm and stir every 30 to 45 minutes for party service without drying out.
