In a large pot or skillet add 2 tablespoons of canola oil on high heat.
Season the pot roast with the salt and pepper.
Add the pot roast to the pan and brown on both sides, 3-5 minutes on each side.
Add the meat to the slow cooker.
Add the onions into the pan you browned the beef in and cook for 1-2 minutes.
If you have space around the meat in the slow cooker add in some small potatoes and carrots.
Top the beef with the onions, garlic, thyme, and bay leaf.
In a small cup add the beef base (if using) to the balsamic vinegar and whisk.
Top the beef with the balsamic mixture, red wine, and brown sugar.
Cook on low for 6 to 8 hours.
Remove bay leaf before serving.
To make the sauce into a glaze, strain the liquid out after it is done cooking.
Spoon off the fat and discard.
Add the remaining sauce to a small pan and cook in a saucepan on medium heat until thickened, about 8-10 minutes.
If you want a stronger balsamic flavor, add in another 2 tablespoons of balsamic vinegar to the sauce before cooking it down in the saucepan.