If you need to mapmaker a secret base on one of you survival worlds, here is how to do it:
Step one: Create a tunnel to where your base is or where it is going to be.
Step two: Place temporary ladders into the tunnel. On the first bottom block place any kind of track.
Step three: Climb the ladders and then delete them. At the top of the tunnel, looking down, place a minecart on the track.
Step four: Then place a preferred block that blends in with it's surroundings.
Step five: Try it out. Hold down the block which your minecart is underneath and you should be teleported into the minecart.
Step six: Fill your base with all your treasures!
Hope this helped