Kodama of the East Tree and Scute Swarm on the battlefield.
Steps
Play Boros Garrison.
Kodama of the East Tree, Boros Garrison, and each Scute Swarm trigger.
Resolve the Kodama of the East Tree trigger, not putting anything from your hand onto the battlefield.
Resolve the Boros Garrison trigger, returning it to your hand.
Resolve each Scute Swarm trigger, creating a token copy of Scute Swarm if you control six or more lands, or a 1/1 green Insect creature token otherwise.
Kodama of the East Tree triggers for each token that entered the battlefield.
Resolve all but one of the Kodama of the East Tree triggers, not putting anything from your hand onto the battlefield.
Resolve the last Kodama of the East Tree trigger, putting Boros Garrison onto the battlefield from your hand.