Sure. I'd use sand or corn meal rather than flour. Flour makes a mess when wet.

Or you can simply draw lines or poke small holes in the flats to determine your plant spacing. I have seen folks cut a piece of tissue paper to fit the tray, mark spacing on it, lay it on the tray and punch holes through it with a pencil or similar. Drop in the seeds and remove the paper. :)

Dave

No flour please ;) When I was a kid, I can remember sitting at the kitchen table doing paper mache and art projects with the budget glue we could afford....flour and water. It didn't set up as clear as Elmer's, but was just as hard when thoroughly dry.

I'd 'draw' lines on the flat. And if you've over seeded - that's where thinning comes in later. Simply use scissors rather than pull excess seedlings out disturbing their neighbors.

I understand your dilemma. I should think that sand would work just fine. I usually start seeds inside myself. A sunny location and some heat does the trick.

You might enjoy a book by Eliot Coleman who teaches organic farming at College of the Atlantic in Maine. He gardens year around with out heating his green houses as did Helen & Scott Nearing. Their book is called Living the Good Life, How to live Sanely and Simply in a Troubled World. They farmed in Maine also. You can purchase them used for less than cover price at Amazon which is what I did. Good Luck. Hope the onions do great.

patchwork, please use a very light hand with the corn meal. Corn gluten is a natural germination inhibitor. Pure corn gluten is sold as a weed and crab grass preventer (pre-emergent) for lawns, I don't know how much is present in amounts of corn meal.

In the end, I ditched the whole idea and just turned on a VERY bright light. I was able to see the seeds against the potting soil much better than I expected. I anticipate I will still have to thin a bit eventually, but the deed is done!