Open the bag and dump the meatballs into your Crock-Pot.
In a microwavable bowl or glass measuring cup, melt the butter.
Add the flour and microwave on high power for one minute. Whisk, and microwave for one more minute. Whisk again and microwave for one additional minute.
The flour and butter mixture will be bubbly. Whisk in the beef broth until smooth.
Add the cherry preserves, Worcestershire sauce, Dijon mustard and pepper. Whisk again.
Pour the sauce over the frozen meatballs.
Cover and cook on low heat for 6 - 8 hours until the sauce is thickened.
Stir in the sour cream until smooth. Keep warm until ready to serve.
The meatballs need to have an internal temperature of at least 165 degrees F before eating.
Serve the meatballs and sauce over mashed potatoes or buttered egg noodles, with a side of green beans for a complete meal.