My partner ran out of pots, while replanting seedlings, so I designed this quick to print flower pot to print a few extras. It does the job. Although, you might want to prop it up a little bit, so water doesn't pool under it, but for seedlings, that will grow out of the pot quickly - this does the job.

Also it's almost as flexible as the plastic pots you buy in any gardening store. So it's easy to squeeze it and loosen the dirt when replanting.