Breath of Fury attached to another creature you control that does not have summoning sickness.
Slimefoot and Squee does not have summoning sickness.
An opponent cannot block and kill creatures you control.
Declare the creature with Breath of Fury attached and Slimefoot and Squee as attackers.
Slimefoot and Squee triggers, creating a 1/1 Saproling creature token.
Deal combat damage to an opponent using the creature with Breath of Fury attached.
Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the Saproling token, then causing you to untap all creatures you control and to get an additional combat phase after this one.