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 my first time growing from seed and I haven't transplanted yet, but my friend has been using them successfully ๐คท๐ปโโ๏ธ she's the reason I'm doing it that way (and me having no money lol)
It may depend how sturdy your brand of cardboard packaged eggs are I guess