The pre-built STL files let you print a 12-pot seedling starter. Each pot has drainage holes at the bottom to let excess moisture out, and a tray to catch any leaks. Use the muddler to create newspaper inserts which can be planted directly in the ground, making transplanting easier. You can also use the newspaper seed pots without the planter if you want. See the PDF instructions for more information.

The attached OpenSCAD file is parameterized to let you fully customize the planter: change the number of pots, pot size, number and size of drainage holes, and many other things.

You should plan to print the muddler with supports; the other parts don't need it.