Volumetric style eating.
For breakfast, I can saute onions, mushrooms, peppers, spinach, etc and make a huge egg or egg white scramble for 100-200 calories, and even add cheese if I want.
Lunch could be 1-2 cups of a pureed vegetable soup or a veggie-strong chili for less than 200 calories.
Dinner may be a huge bowl of zucchini noodles with marinara and meatballs or alfredo, a huge veggie stir fry topped with fish, or even a huge bowl of curry over cauliflower rice. Each of these are around the 200-300 calorie range.
I don't like being hungry, so I just eat a lot of vegetables in my meals to fill me up.