All ballots (and everything else) must be tracked, secured, and accounted for thru the entire process. This verifies the entire physical chain of custody. All materials and records are audited by the canvassing board before an election is certified.

Your election administrators probably have their procedures available online. And everyone is allowed to observe any part of the process. I strongly encourage you to observe and participate. Attending the canvas board meetings are quite illuminating.

Source: long time poll judge and election integrity activist.