Overnight oats
Fiber comes in 2 forms. Soluble and Insoluble. The body can use either to help wastes move though the system. Soluble like the pectin found in apples or oats, work by helping the water content. Insoluble like celery, asparagus etc, add bulk.
Then as with everything we eat... how much is a key.
Personally I will occasionally add steel cut oats to my breakfast for the added fiber. That meal will be an egg over easy, 1/8 cup COOKed steel cut oatmeal, and an ounce of kimchi. I make a single portion of the oats, which is 1/3 cup of oats to 1 1/2 cups of water boiled for almost 30 minuets. I then pour the oatmeal into my 4oz ziplock container making sure I fill them 1/2 full yes... 2 oz liquid volume. For me that is a day's worth of starch. I further don't eat the oats every day.
I choose to limit my starches, because we do need carbohydrates... as even lettuce has carbs and lettuce is good for humans. Wheat, rice, oats, rye, potatoes, yams, sweet potatoes etc. are the issue. A little bit leave us wanting more, and the body stores that stuff away (on our hips) for a rainy day.
Best of luck.
It is better to travel and get lost...
Than never to travel at all.