Instructions
Chop down trees with your axe to gather as much wood as you can. It's preferable to have at least 20 to 30 wood blocks on hand.
Bring your wood to your workbench. This is where you can craft your wood into the items such as signs and hatches.
Craft two signs and three hatches at your workbench. There are various ways to build a desk using wooden supports and wooden platforms, but the sign/hatch method tends to be easier for beginners to figure out and looks clean once it's set up.
Place a sign in one corner of the desired room once you've finished crafting them. You can write something on it if you want, but it usually looks cleaner if you leave it blank. This will be one end of your new desk's support. Top it off with a hatch.
Connect two more hatches to the one on top of the sign. The hatches can be in a row or in an L-pattern, depending on how you like your desk to look.
Place your final sign under the hatch at the other end of the desk from your original sign. You should have a "Minecraft" desk.