How do you get a 3x3 craft in minecraft?

First, punch a tree until you get a block of raw wood.

Place the one wood block into your 2x2 Crafting box and you will get 4 wooden planks.

Put one into each slot in the 2x2 grid, and you will get a workbench, place it somewhere in your world, and right click on it to get a 3x3 Crafting box.