Right after spawning in Santa´s Workshop, grab the TNT, light it up using the chimney and hold it. Blow yourself up.
After dying, you will respawn. Grab another TNT and do it again.
Explode three times for good measure.
Go to the Punch-O-Matic and finish the level with the button "I don´t care. I´m done here and the union´s got my back..."
Remember that this will get you fired and your office will reset, deleting all your trophies, so don´t try this achievement if you are currently gathering trophies for an specific achievement.