Step 1:
Go to the End, it doesn't matter if you use a stronghold or build a portal.
Step 2:
Place a Nether portal in the End with the setblock command:
Step 3:
Go through the nether portal. You will end up in the Overworld, and after a few seconds, you now can't mine, place blocks, hurt mobs, or modify the world in any way, shape or form. If you are in Creative mode, you can still fly around, but the world itself can't be modified.