Activate Selvala by paying and tapping it, adding at least 1.
Activate Yahenni twice by sacrificing Selvala and Slimefoot and Squee.
Activate Slimefoot and Squee by paying 1 and sacrificing a Saproling, returning it and Selvala from your graveyard to the battlefield.
When Slimefoot and Squee enters the battlefield, it triggers, creating a 1/1 Saproling creature token.
Repeat.
This loop relies on a clever cycle of sacrifice and rebirth enabled by Slimefoot and Squee, which uses its recursion ability to pull itself and Selvala, Heart of the Wilds straight back from the graveyard. While Kratos, God of War grants all creatures haste right from the start, Selvala pays for the resurrection costs by tapping for an abundance of green mana, fueled by the rising power of Yahenni, Undying Partisan. As Yahenni and Slimefoot and Squee cycle in and out of the graveyard, the constant arrivals and sacrifices generate an endless supply of Saproling tokens and death triggers to fuel the engine indefinitely.