When a Witch builds a doll she builds the head first. In part because the head is the hardest, the most full of interlocking spells and clockwork. But also because part of building a doll is raising a doll.
A good witch takes that head and swaddles it against her while she works, shows the doll-to-be how to make tea, how to hoe and weed the garden, where the linen cupboard is. The new doll soaks up this information with avid attention; what else can it do?
The close, constant skin-to-porcelain contact also bonds the doll to its witch, so it will always obey and can never betray her. Imperfect Imprinting creates Defective Dolls, as they say!
Some unscrupulous witches will have their dolls make dolls, or do as little to imprint as possible, aiming for quantity over quality but they are shunned by polite society and for good reasons: doll mills are the number one source of feral dollpacks.
This is also why the best way to calm an agitated doll is to put its head in your lap: it’s most soothing from its witch, of course, but it always reminds it of this time when nothing separated it from her.