How to hover minecraft using command blocks

You can place a block under the player 20 times a second. To do this create a command block tick clock that executes the command:

execute @e[name=<player name>,type=Player] ~ ~ ~ setblock ~ ~-1 ~ minecraft:sandstone

This is possible in the 1.9 snapshots.

The command is

/effect @a levitation 1000000 255 true

This will produce a hovering effect. You can't go up and down, but it achieves what you've requested.

Also, the question is worded oddly, and doesn't completely make sense.

If you want a version that allows you to traverse down the Y axis, then try this

/effect @a levitation 1000000 252 true

This gives the player a slight downward movement. If you want to go up, try

/effect @a levitation 1000000 2 true

This is all I can help you with unless you specify in more detail what you want.

Note: If you want it to be like creative mode flight, I can put something together for you.

I haven't tried this but I will assume it works in almost all versions.

Set up a clock circuit with a command block attached and put this in it

/tp <Name Of Player> ~ ~<blocksToBeLifted> ~

Replace with the height above the ground you want the player to levitate. Make sure you test it first because the clock circuit might go to fast and lift the player up blocks faster than they fall (so they will continuously go up)

In short this command constantly teleports the player upwards. Just remember you need to have a ~ before the amount of blocks you want the player to be lifted. To stop the player from floating just stop the clock attached to the command block.

Sorry if I didn't answer your question correctly, didn't really understand it properly!