Seedling pot made from an empty toilet paper roll. After germination, it can be buried directly in the garden bed as is; the roots will grow through the softened cardboard, and soil organisms will then consume it. Make sure to only use toilet paper rolls made from unchlorinated and unprinted cardboard.
edit: please check if recycling has a problem with chemicals or heavy metals in your country
This is a good idea, but I might use more durable paper towel rolls cut in half instead. All the world's toilet paper is soaked in a special form of PFAS/forever chemicals that make paper much more soluble in water, or less likely to stick to equipment during manufacturing. That chemical can bioaccumulate in plants and soil, contaminating it for decades, unfortunately.
https://www.theguardian.com/environment/2023/mar/13/toxic-forever-chemicals-pfas-toilet-paper