Introduction: Pig Floor
The pig floor doesn't need to be made out of pigs. It could be zombie, villager, basically anything other than creepers(if you do it won't last long
Step 1: Dig Down 2 Blocks (or Three If You Need)
Step 2: Dig As Far As You Want Your Hallway
Step 3: Put Whatever You Want in the Pit
Step 4: Put Glass Over the Pit
After you are done with this you might want to make a hallway. But because it was just for you guys and temporary, I'm not making one