Make a door frame.

You can make one yourself or just follow my build.

Be sure to place down the iron door like this.

Dig underneath the block where the door is sitting on and put down a redstone torch.

Put in the command I'm putting in to get a command block.

Place two command blocks somewhere near the door and make them both from impulse to repeat.

Press F3 then look where the arrow is pointing.

Now look at the torch's hitbox then paste the command from the video's description into the chat.

Change the ITEM to the item/block you want to hold to close the door.

Now change the coordinates to where the torch is, which is also where that arrow is pointing at.

Ctrl+A then Ctrl+C to copy the command line then go to one of the command blocks then paste it into one with Ctrl+P.

Okay, now be SURE to activate that command block with a redstone block or torch.

CrtlA CtrlC the first command line then take it to the other with CtrlP, changing TWO THINGS: The item you hold to OPEN the door then redstone block to air.

Then activate that command block too.

That is pretty much it.

I've long realised my voice is so boring but anyway, you build a corridor to make it look nicer.

Great, now I can be alone :)