Doors shut and locked. Reconnect battery, open doors with fob or handle with fob in range, should shut off alarm. If doors are unlocked when battery was disconnected, car probably thinks it's being stolen/normal alarm behavior
So what I'm doing is....I have a battery disconnect switch. I have the trunk open, then lock the car using the FOB. Then I pull the plug and shut the trunk. To reconnect the switch, I have to pull out the physical key, open the door and crawl back to the trunk area to reconnect the battery- that's when the alarm goes off. I'll try doing the opposite- leave the car unlocked, and disconnect the battery first, to see if that makes a difference.