Simple Flush Piston Door

You can use this to hide your base or really anything you would like to use it for.

You will need: Unspecified amount of random blocks, 12 sticky pistons, 6 redstone dust, 2 redstone repeaters, and a source of redstone power (levers, buttons, redstone blocks, etc.).

Make or find a wall (It doesn't have to be iron) and break open a 2x2 square. This will be where the door is.

On the inside put four pistons on each side like this.

Add 2 pistons as shown, facing toward the door.

Put two blocks in the space in between the pistons (First image) and then put seven blocks along the top (Second and third image).

Add redstone along the top as shown.

Add two redstone repeaters like this on two ticks and facing outwards.

Now make an input connecting to one of the 2 pieces of redstone dust in the middle. Make sure it doesn't touch any of the pistons.

Power off...

Power on!

One lag I experienced was the delay for the redstone repeaters wasn't working so it pulled back the blocks but didn't pull them aside. How I solved it was I just move where the lever or button was. If it was on a block I would just remove the block. Hope this helped.