Once the water is bubbling, gently place the prepared vegetables into the steamer basket. For best results, stagger the addition of vegetables based on their density. Begin with firmer items like carrots, broccoli, and cauliflower, letting them steam for a few minutes before layering in the more delicate vegetables such as green beans, zucchini, or bell peppers. Cover the pot tightly with a lid to trap the steam and cook until the vegetables are tender-crisp—cooked through but still retaining slight firmness. Cooking time will vary from 3 to 10 minutes depending on the type and size of the vegetables. Test doneness by piercing with a fork.