I designed these as a way to start seedlings on the Beaver Plastics lettuce floats with ~1" 

openings. Any rafts with 1" holes will work. It also works well in 2" tubes with 1" holes
drilled in. If using a larger tube, the water collection tube might not reach the reservoir.
If you are looking for something like this, but these dimensions don't work, let me
know and I will configure something for you.
Put a cotton ball or some rockwool in the bottom so the container will hold
the media, then follow basic seed planting instructions. I am sure other things
(ex. hemp rope, newspaper) would work as well. Add planting media ( I use
50% coco fibre and 50% perlite), water down media or wait for the media to
absorb from the water tube, and then follow seed planting instructions.
If you end up printing this Thing and liking it, please donate! I am a creator, and would appreciate the donation immensely.

Education: These will also work for a larger mouthed container such as a Snapple or Sobe bottle. A rayon string or sheet of cloth can be added to make a very basic NFT planter for use with seedlings in a classroom environment. Consider making a terrarium using a 2 liter bottle if not used in a greenhouse.