Cast Clockspinning with buyback by paying ({3} magic symbol) ({U} magic symbol) .
Poppet Stitcher triggers, creating a 2/2 Zombie creature token.
The Zombie enters the battlefield, triggering Mana Echoes, adding at least ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Resolve Clockspinning, allowing you to give or remove a counter from a creature that has a counter on it and returning Clockspinning to your hand.
Activate Phyrexian Altar by sacrificing the Zombie, adding ({U} magic symbol) .