What layers make up a properly built bocce court?

A regulation-quality bocce court is five layers: a graded and mechanically compacted subgrade, 4–6" of crushed structural base that also drains like a French drain, a 2–3" decomposed granite leveling course, a 1–2" oyster shell or bocce blend playing surface, and anchored side boards containing it all. Every lift is compacted with a plate compactor or vibratory roller. Skipping the leveling course lets the fine surface migrate into the base and the court goes uneven within months.