Slow digestion? Tips reasoning

Could it be food intolerance? anyone have anything they do to speed up digestion or make sure you completely empty your stomach for check ins? Could it be a veggie causing this meal timing etc not constipated just seems my stomach isn’t flat some days and i could empty it more . Thought about trying a fiber supplement like fiberlyze to get things moving . Also i eat about 250-300g veg a day