Open the crafting table (4×4 grid)
Place 5 wooden planks in a U-shape:
Top row: planks in slots 1, 2, 3
Middle row: planks in slots 1 and 3 (leave center empty)
Bottom row: leave all slots empty
Craft the boat
Move the boat to your inventory
Place the boat on water by aiming at the water and using/place (right-click or use button)