I'm a first time DM for experienced players. A Halfling Ranger, Half Elf Monk and a Tiefling Monk along with a NPC Gnome Acolyte. They are playing The Sunless Citadel out of Tales of the Yawning Portal.

After fighting and killing Dragon Wyrmling, and losing the Koblod Meepo, the players move to a hallway the the room connects to. They proceed down the hallway to the door on the far side.

Half Elf (OoC): I don't listen to the door and open it.

Me: You open the door to the Goblin Colony.

Half Elf quickly thinking trying to distract them: I have come to release you of your mortal coil!

Tiefling: I quickly cut off Meepo's head and throw it into the Goblin Colony and say, "Yeah, like this guy!" *Rolls crit fail*

Me: Instead of Meepo's head you throw a Goblin's into the room. *Rolls Goblins' fear check as a group and gets a Nat 20* Okay......All the Goblins, even the Non-Combatants, take up arms against you all.

Half Elf (OoC): Even the kids?

Me: Kids, Women, Elderly, ect.

Half Elf (OoC): I close the door and brace myself against it!

Tiefling (OoC): I assist!

Me: Okay. *Rolls* An axe head starts to pierce through the door.

Roll a natural 1 and fall off a wall you were scaling or miss that crucial last hit on the dungeon boss... that dice needs to be punished. Send it to jail.

You can make your own DIY dice jail with these instructions for only $3 (assuming you already have some basic tools)

You will need a 1/2 inch square dowel (about $1.50 at a home improvement store) and 3/16 inch round dowel (about $1.00 at a home improvement store)

You will also need:

A drill with a set of drilling bits

Wood glue