Rinse the lentils and place them in a large crock pot. Add the carrots, zucchini, celery, onion, tomato, and vegetable stock. Cook on high 4-5 hours and on low 7-8 hours.
minutes before serving, heat olive oil in a medium skillet on medium heat. Add the sausage and cook until browned and crumbly. Right before it's done add the minced garlic and stir until combined. Add browned sausage to the crock pot and continue to cook for 30 minutes.
Serve warm or store in the freezer for up to two months.