Activate Selvala by paying and tapping it, adding at least 1.
Activate Phyrexian Altar twice by sacrificing Selvala and Slimefoot and Squee, adding .
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 brilliant loop uses Phyrexian Altar as both an immediate mana source and a sacrifice outlet, turning the death of your board into the fuel needed to recur it. With Tannuk, Steadfast Second granting your creatures haste alongside its other properties, Selvala, Heart of the Wilds can tap for massive amounts of mana the moment she returns to the field, easily covering the activation costs. Finally, Slimefoot and Squee orchestrates the entire resurrection cycle by bringing both itself and Selvala back from the graveyard while leaving behind a fresh Saproling token to repeat the process indefinitely.