How do I make floating sand?

I want sand to just hover in midair and not immediately fall after being placed. Is this possible?

Solution 1:

How to create true floating sand

This answer is for how to truly make sand float, and only works for 1 sand block. If you need more than one sand block, true floating sand is not the option for you. See my other answers listed below for the option that best suits you.

Place a door on the ground.
Place a piece of sand on the door.
Break the door by its bottom half. (click on the bottom of the door, not the top)

Notes

If you need to place more than one floating sand block next to each other, it won't work. Breaking a door will update the sand blocks diagonally, which means you can't. Consider using a different strategy. I've posted different solutions that may suit you better.
Make sure all the surrounding blocks are in place before you break down the door, too! Placing/breaking any block adjacent to the sand will update it and cause it to fall. If you need to change things without making the sand fall, put a door underneath the sand before making changes.

Tips!

String causes an update when you step on it, even if it's not connected to tripwire hooks. This means that a floating sand with string on top will fall when a player steps on it. This can make for some evil, almost undetectable traps!
In Java Edition, this used to be accomplished using a double-tall grass/flower. However this functionality has been removed.

Learn more about sand and string on the Minecraft Wiki:

Sand
String

Solution 2:

How to create a sand trap using signs

This option is best if you want to be able to have all the sand fall by breaking one block. See my other answers for other options and choose the one that suits you best.

You need a support block. Do not place this block in the way of the sand.
Place more signs on the sides and front of the first so that the area covered by the signs covers the whole pit.
Place sand on top of all the signs.
To trigger the sand trap, break the support block.

Solution 3:

How to create semi-floating sand using string

This is your best option for placing more than one block of floating sand next to each other.

Place a piece of string one block below the location you want your floating sand to be.
Place the sand on the string.
Repeat for each sand block.

Even updating the string by placing/breaking auxiliary blocks will not cause it to fall. The only way for the sand to fall through the string is if the sand falls into it from a greater height.