Driving between counties with it in the car: what is the actual rule

genuine confusion, not looking for a loophole. i am in the car constantly, different county most weekends, trailhead to trailhead. so there is a thing i do not understand: what is the correct way to have it with you in a vehicle here. sealed? trunk? does the county i started in matter, or the one i end up in? everything i find online is either a lawyer ad or somebody very confident in a comment section, and those two sources disagree. i would rather be boringly careful than confidently wrong, so i am asking. if someone can point me to where this is actually written down rather than telling me what they heard, that would help a lot.