Once it comes to a simmer, cook the stock for 1 hour to 1 hour 20 minutes. If you are not sure if it is done you can taste a chunk of carrot to see if it still tastes like carrot. If it does, simmer for another 10 to 15 minutes. If it tastes like veggie stock, all of it’s flavoring potential is spent and you are now ready to move on to the next step.