Activate Selvala by paying and tapping it, adding at least 1.
Activate Umbral Collar Zealot 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 clever loop turns the graveyard into an engine by cycling your key permanents in and out of play. Slimefoot and Squee acts as the primary reanimation hub, paying its activation cost using mana generated by Selvala, Heart of the Wilds while bringing both itself and Selvala back to the battlefield. Meanwhile, Umbral Collar Zealot provides a reliable outlet to bin creatures and sculpt your draws via surveil, and Frostcliff Siege rounds out the board by granting your creatures haste, trample, and a power boost to keep Selvala's mana production flowing at maximum efficiency.