How are tonsil stones started?

Cryptic tonsils. The first thing that starts are tonsils that have deep pockets or crypts. Food, debris, and bacteria get trapped in the crypts and form the "tonsil stones.".
Mouth bacteria. Most tonsil stones aren't from food or other particulates. Tonsils have crypts or crevasses into which a mouth bacterium, actinomyces, can enter. As the bacteria proliferate they create debris that under the microscope that look like sulfur granules.