Heat the olive oil in a large Dutch oven or stockpot over medium heat.
Add the garlic, onions, celery, and carrots. Cook until softened, about 5 minutes, stirring often.
Add the water, frozen vegetable scraps, bay leaves, parsley, and thyme. Reduce heat to low and simmer, partially covered, for 45 minutes.
Pour the broth through a fine mesh strainer into a large heat-proof bowl or pot; discard solids.
Once the broth has cooled, transfer it to airtight plastic containers or freezer bags and store it in the freezer. (I usually freeze it in 2-cup portions so I don't have to thaw all the broth every time I use it.)