Open a Crafting Table
Place 2 sticks in the left and middle slots of the top row
Place 2 sticks in the left and middle slots of the middle row
Place 2 wooden planks in the right and middle slots of the top row
Place 2 wooden planks in the right and middle slots of the middle row
Take the fence from the result slot
Use 4 sticks and 2 matching wooden planks to craft 3 fences