How to build blocks directly under your feet in minecraft?

Jump. When you're at the highest point of your jump, right click with the block in your hand at the ground below you. Make take some practice if you want to "pillar" your way up to the sky quickly.

Jump n place

On pc just repeatedly press the space bar and right mouse button.

Jump and click or tap for the pocket edition.

1. Have the block in hand.
2. Point your camera at your feat.
3. Jump straight up.
4. Place the block while you are airborn.

Done right you should land on the new block. It will take a little practice to get the timing right, and there will be occasions where you still mess it up, but it isn't that hard.

The technique is also called a 'nerdpole'.