Set aside the non-dairy milk and cornstarch. Next add all remaining soup ingredients to a slow cooker, making sure to put the onions, potatoes, and carrots at the bottom where the pot stays the hottest. Cook on low for 6 1/2 - 8 1/2 hours (or on high for 3 - 5 hr).
After 6 1/2 hours (3 hr if cooking on high) remove the lid from the slow cooker and check to see if your potatoes and carrots are soft. If veggies are still firm, replace lid and cook longer, checking every 30 minutes (or an hour if they aren't even close to being done, though they should be), until veggies are no longer firm.
Sift the cornstarch into a bowl or cup with the non-dairy milk and whisk until no lumps remain. Stir the cornstarch/milk mixture into the soup. Taste soup and adjust seasonings as desired. Turn heat to "keep warm" and let sit another 15 - 30 minutes, or until ready to serve.
To serve, ladle soup into individual bowls and eat as is or top with my tofu "bacon" crumbles, or toppings of choice.