To prepare an area for growing onions, carefully rake over and remove as many weeds as possible. It will be difficult to weed until the onions seedlings are high enough to easily recognise.The area should be well draining, and not heavily fertilised, as the bulbs will not cure properly if over fed. Create shallow furrows approximately 25cm apart. To sow onion seeds, mix a packet in with clean river sand. This makes it easier to sow and space out the seeds, as well as being easier to see where you have sown!
You can then either gently pour out of the container you mixed in, or put into a brown paper bag and snip off a bit of corner (think of it like piping icing), letting it trickle out of the hole. Using the back of the rake, gently pull across the top of the furrows, which will cover the seeds, and water in, even if the soil is damp.
Onion seeds are slow to germinate, it may take two or more weeks for them to sprout, and they take about 6 months to grow to maturity. Before the days of iPhone calendars and applications that told you everything (I wonder if there is an application for sowing?), people used to sow seed on the shortest day of the year, and traditionally harvest on the longest! You will need to thin when the seedlings are about 5-10 cm high so that each seedling is approximately 10cm apart. I prepare a second bed for onions when I am going to heavily thin out, and transplant the stronger ones. These transplants will mature at least a couple of weeks later than those left in the original location, but you will waste far less seed! I'll post at a later date on harvest and storage, but for now, get those onions in!