the 2x2 hidden door is pretty compact, I will add a video tutotial link how to build this.

I also will add a redstone device that lets you switch between open/close mode, this is however not included in the video.

All redstone is shown and not hidden so it is pretty easy to copy.

1: unzip the .zip file
2: read the read me file in the .zip
3: place the world save in the .minecraft folder.
                         ( windows sign + r  -> %appdata% -> .minecraft -> saves)

the link to the video tutorial: www.youtube.com/watch?v=oHUxvivSWcI&feature=youtu.be
and my channel: youtube.com/user/TheMcplayer64