Farmland only stays hydrated within 4 blocks of water, so the shape of this layout isn’t arbitrary — it’s the largest square a single water source can fully cover.
Step 1: Dig the water channel
Dig a cross-shaped trench through the middle of a 9x9 area and place your water source in the centre. Water spreads outward automatically to fill the channel.
Step 2: Till the surrounding soil
Use a hoe on every remaining block in the 9x9 area. Anything within 4 blocks of the water (which this whole layout is) will stay hydrated permanently.
Step 3: Plant
Plant whatever seeds you’ve got — wheat, carrots, and potatoes can all share the same plot without issue.
Step 4: Optional — fence it in
A simple fence border keeps mobs from trampling crops at night, though it’s not strictly necessary if the area is well lit.