Prepare a garden's soil by loosening its top layer with a rototiller or rake. Till the garden's weed or other plants under the soil surface. Flatten the soil surface by using a rake.
Broadcast oat seeds on the soil surface, throwing one handful at a time in front of you. Aim for using about two seeds per every 1 square inch. Don't worry too much about the exact number of seeds per inch, but try to spread the seeds as evenly as possible.
Rake a thin layer of soil gently over the seeds, covering them. Oat seeds germinate without the soil layer, but the layer offers protection against animals that may eat the seeds.
Water the soil, using water from a garden hose that has a nozzle adjusted to the mist setting. Water helps the seeds settle into the ground. Check the soil's moisture level every day, and keep it moist until the seeds begin to sprout.