Soap the printed cases, close them, mix the plaster by weight, pour it, and let the mold dry before its first cast.
The printed cases shape the plaster; the dry plaster is the mold. The pour sheet of your piece has the amounts and these steps, worded for its own mold.
Brush mold soap inside every case, and on the lips of the edge frames, wipe the foam off with a damp sponge and let it dry for a few minutes. Do this three times. It is ready when water beads on the print. Without it the plaster grabs the print.
Cases printed in one piece have no clamps and no cut faces: stand them level, open face up.
If you chose printed natches, press one nipple-first into every round cup on the case floors and push one socket-first onto every peg, each seated flat. Keep them free of soap, so the plaster grips them.
Weigh the water into the bucket and the plaster beside it: the pour sheet gives both, 10 % extra included. Sift the plaster onto the water, let it soak 1 to 2 minutes, then stir 2 to 3 minutes without whipping in air. Mix one batch per piece. Dry plaster is a fine dust: wear a mask while you weigh and sift.
Rinse the bucket and tools in a second bucket of clean water, never in a sink: plaster sets in the drain.
The plaster stays pourable for about 5 minutes. Pour a thin, steady stream into one corner, so the plaster rises and pushes the air out, up to the top of the edge frame, then tap the table to bring up the bubbles.
Leave it 45 to 60 minutes. The plaster warms as it sets: wait until it has cooled again, or it grips the case. Take the band off, slide the clamps back up, lift the edge frame off and pull the two halves away from the plaster. A case of one piece you turn over, flex its walls and ease the plaster out. Wipe the casting faces with a clean, damp sponge to lift the soap film.
Put the pieces together, band them and leave them somewhere warm and airy, under 45 °C. Four days is the least; a cool or damp room takes a week or more. Dry plaster no longer feels cold, and a damp mold will not cast.