Puppeteers like Nadia use bodies, body parts, rare minerals, and other materials to create puppets they can control. Of course, Nadia is a unique case in this regard.
However, she also requires schematics to create these puppets. Without the schematic, she couldn't create even a single puppet.
She had already complained to Klaus about this. She needed the design like the way swordsmen need their sword skills.
This is the way of her craft, and the same applies to other professions like Necromancy, where one either summons the undead, raises them from the dead, or, in some cases, creates them.
The core of it all lies in creation and hoping for the best.
You wouldn't have full control over what their existence should be like or what they should stand for. The further you progress, the more you can ensure their personalities align somewhat with your own.
Creation, in this sense, is largely random.