It takes 6-12 hours to break down your food depending on your constitution. Within that timeframe is awaiting the hunger trigger. This trigger signifies the body is ready to eat and most importantly that the previous meal has been digested. It usually happens when the load is ready to move through the large intestines.
If you snack and break your natural process, you turn your previous meal into toxins.
You might eat four smaller meals/day if it suits your constitution or you're weaning yourself off snacks, but they are meals, with all the meal rules that come with them.
There are no healthy snacks.