Sauté veggies. Start by bringing your stockpot or Dutch oven to medium-high heat with 2 tablespoons of olive oil. Once the oil is brought up to heat and just about to smoke, add 1 cup of diced yellow onion, ½ cup sliced celery, and ½ cup diced green bell pepper. Sauté the veggies until fragrant and tender, about 4 to 5 minutes.