Seedlings need a more gentle microclimate to grow than older plants. This often means a shadecloth structure to reduce hot sun and wind, which can kill young seedlings. Both will cost money, so consider this before growing seedlings on any scale. You can use basic seedling trays or seedling pots, which are also cheap. But the type of soil or growing medium you use is very important.
Ordinary topsoil may crack and dry out or may contain insects and diseases which will flourish in the ideal microclimate. Obviously, this will mean you won’t get good results with the crop. If you can afford it, buy potting soil. The expense is justified by results. But if you can’t or don’t want to, you can make potting soil yourself. Depending on your climate and the plant variety, planting times may be different. Read the back of the seed packet for details.
Fill the tray with your growing medium by sifting it into the tray. Fill it up until it overflows, and then lift the tray a little and tap it against a solid surface to settle the medium.
Level the soil with a striking board. Drag the stick or striking board across the top of the tray to make sure the soil is level and evenly dispersed. You can also use your hand. Take about 1cm of soil off the top.
Press the soil down with a firming board or your hands until the top of the board is level with the top of the tray.
Moisten the soil using a watering can with very small holes.
Now to sow your seeds. Pour some into your hand. Sprinkle on top of the soil, leaving a little space between each. This space depends on the plant; read the seed packet instructions.
Cover the seeds by sieving a light layer of soil over the tray. In general, seeds should be covered with soil to a depth equal to twice the size of the seeds, but check the packet for exact information.
Compact the soil by using your hands or the firming board to gently, but firmly press the soil down over the seeds.
Seeds need good soil contact to germinate properly.
Label the tray using a permanent marker to write the variety planted on one side of the label and the date planted on the other side. The temperature, amount of sunlight and water that the seeds need will be included in instructions on the packet.
Sources: The New Complete Book of Self-Sufficiency by John Seymour, Wikihow – How to plant seeds in a basic seed tray.