Place roast in the slow cooker and place carrots around the roast.

In a bowl, combine the cola, brown sugar, chili sauce, ketchup, and onion soup mix.

Cover and cook on low for 8-10 hours.

Remove the roast from the pot. Then remove the carrots with a slotted spoon.

Remove some of the juice leaving only the amount you think you will need to make the sauce with for the roast.

Mix 2 Tbsp of cornstarch with 2 Tbsp of water. and add a bit at a time to the juice to thicken. Add enough to reach desired thickness. If needed, you may need to make some more cornstarch water mixture, depending on how much juice you save.