1 old nylon stocking (or a new one; they're less likely to have big holes).
Note: this is easier with two people.
    Person 1 puts both hands in the stocking and holds it open, pushing the bottom flat against the ground or table. Person 2 pours the grass seed into the stocking, spreading it around evenly (you don't want any bald spots). Then Person 2 stuffs in the potting soil until the stocking is the general size and shape of a head. Person 1 removes their hands, and someone ties off the stocking with a rubber band (trying to keep the knot to one side so it isn't visible from the front). The trailing stocking is cut off close to the knot. The other three rubber bands are then used to tie off ears and a nose by pinching a clump of soil through the stocking, twisting it tight, then applying the rubber band. The ears and nose can be shaped to look like someone in particular, as can the entire head (some people have very distinctive head shapes). The googly eyes are then glued on (I recommend using superglue, since normal glue tends to let the eyes slide down the face). The puff paint is then used to draw a mouth and whatever else is desired (glasses, freckles, eyelashes, tattoos, etc). For one chia head, you will need:
1 handful (or thereabouts) of grass seeds, whatever kind you like.
Enough potting soil (or plain dirt if you don't have any) to fill the stocking.
4 tiny rubber bands, about the size of the kind used on braces, maybe a little bigger.
2 googly eyes (the kind where the eyeballs move).
Enough puff paint (or something similar) to draw on a mouth and anything else you want.
1 sense of humor per person.
   
And now the chia head is ready! Let the glue and paint dry, then put the head in a dish of some sort with water at the bottom (make sure there's always about an inch of water). Put the dish where you want, and in a few days green hair will start growing. (Tip: haircuts are fun. You can practice different hairstyles: mohawks are particularly entertaining.)
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