Note it is PE NOT PC I don't have cauldrons and all that. Don't judge me! And it's my first instructable so I don't know how to do this.
Find a clear spot. I'm putting mine in a corner.
Now put down a block of nether reactor core.
Now put trap doors around it like this. They will be on the floor at first
Next tap the trap door.
Now put one more trap door on top. This is now the lid.
And there you go! Note I got this idea from someone else. So I don't get much credit. Please leave a comment!