My best seedlings have come from winter sowing in buss tubs, the kind they use in restaurants.
I pack it with potting soil, 50/50 peat and compost cow manure, then I space the seeds all at once using a dibbler I made .
One corner is scooped out and I add a 1 gallon plastic pickle jar, inverted, with a hole in the lid for watering.
This reservoir bottom waters the seedlings and extends the time between watering.
After seeding, I top the whole thing with a second, translucent white bus tub.
When they start to crowd the inside of the tub, I use an old spatula to cut out servings of seedlings and plant them out.
I haven't done a single tub this year 😔, but I hope to get back to it.
I'd like to get away from peat, I'm thinking of using sand or pine bark fines and my own compost instead.
My compost is food scraps, chicken feed, chicken poop and lots of leaves.
It holds water well, and the tubs have been too wet in the past , so amending for drainage might be the move.
I've used gutter mesh to make ~4" air pruning pots , but to work, they need more space than a tub with the same number of seedlings.
They use plastic or aluminum, and are kinda wonky, so buying actual hydroponic cups might be a better choice anyway.
If you don't care about air pruning but you do want to keep seedlings separated, a steel or aluminium can, with both ends cut off, might work.
Sections of downspout, plastic or aluminum, sheet flashing , PVC pipe or corrugated black pipe can all be used for planting pots.
I bet soil cement, especially if reinforced with natural fibers, would make an excellent plant pot.
Break it and discard it anywhere, with no fear of adding plastic pollution to the soil.
The same sort of thing could be made of pallet wood and deck screws(reusable after the wood fails), or staples(cheap and rust away into nothing).
Compost or combust the rotting wood.
I think cylinders made of wine cap mycelium would be my ideal plant pot.
