I agree with Michael, it’s nearly impossible to say “what’s best” for keeping someone full for extended periods of time.
I will say, however, that choosing foods that are nutrient dense would be a good strategy to have. Examples include nuts, seeds, whole grains, or lentils.
For a more complete list, I encourage you to check out the following links:
Which of the foods listed in the links sound especially appetizing to you? Are you already eating some of them regularly?