Me Working on the Stone Mailbox

I am piling up some rocks around the 2' X 2' sand filled base. Then I poured
https://www.amazon.com/gp/product/B0BLY8ZGH8?ie=UTF8&th=1
concrete between the stones.
No one will be able to steal it unless they lasso it and pull it down with a truck. Driving over that pile of stones will damage a vehicle.