When you floss your teeth you remove leftover food and other particles from between your teeth.
Brushing your teeth gets the food particles off of the teeth themselves but simply brushing your teeth cannot remove the food particles that are in between your teeth.
When you don't floss those food particles will remain in between your teeth which can cause mouth odor, tooth decay, gum disease etc.
So it's important to floss your teeth at least once per day and brush your teeth twice per day.
However I recommend you floss after every tooth brushing to keep your teeth clean and healthy.
Going through the extra work of flossing your teeth more often will be worth it because it protects your teeth.
You only get one set of permanent teeth so it's important to protect those teeth.
Gargling with mouthwash or apple cider vinegar is another good thing to kill bacteria in your mouth and prevent gum disease, tooth decay etc.
Also you should oil pull which is pulling coconut oil through your teeth and then spitting it out in the toilet or bucket.
The oil pulling of teeth helps remove bacteria from in between your teeth.