On the world of Ruquelis, about which I have written many times before, there are three sexes, Men, Women and Lilim. Long in the past, the lilim were afraid that their biology was such that women appeared destined to out-breed them (since lilim give birth to 1/4 each men, women and lilim-children, plus 1/4 miscarriages, while women give birth only to 1/2 man and 1/2 woman-children). Out of fear of the extinction of lilim, and because women-children and lilim-children can't be distinguished before the age of 7 to 9, lilim started the practise of forbidding women to reproduce and culling any pregnant and adult women. Over millennia, and with the discovery of a drug called hialutabu which makes all painful stimuli entirely pleasurable, this evolved into the systematic extermination of women by the age of thirty, and across much of Ruquelis, these women were lovingly tortured (subjected to otherwise painful stimuli under the influence of hialutabu that made the experiences ecstatic for the victims) and eaten in cannibalistic rituals.
One of the main reasons for the use of hialutabu and the delayed culling of women was that people on Ruquelis reincarnate and therefore remember their previous lives and deaths. A woman could attend school for the benefit of her next incarnation, and hialutabu made a woman's ritual death the highlight of her life... and helped propagate the desire to continue the practice of femicide and cannibalism.
Since the killing and cannibalism of women is an ancient cultural practice that may be reinforced by memory of a pleasurable death in a past life, many (but by no means all or even a majority) women willingly or even eagerly submit to the procedure. This may be considered similar to the experiences of the Spanish conquistadors with Aztec sacrifices that they attempted to free who demanded to be returned for sacrifice.
However, outside parties who are determined to end the Ruquelians' atrocious, cannibalistic ways have arranged the extinction of the bissuras which were the sole source of hialutabu. Without the drug that makes the Ruquelians' ritual torture and murder of women pleasurable, they can no longer bring themselves to kill their loved ones in the horrific old ways... however, both custom and law still dictate that women must be killed, and cannibalism is still a tradition.
So, until both custom and law can be changed (which will take a while, but is the point of my story) the Ruquelians must come up with a way to kill their women so that they can be prepared for human consumption. The criteria for the 'best' method are:
The method must inflict the least degree of physical pain possible.
The method must inflict a minimum of emotional trauma on the victim.
The method must leave the victim's flesh fit to be eaten as far as practical (the brain and spinal cord are not eaten due to risk of Kuru or similar).
The method should cause the least damage possible to the victim's flesh.
The method should leave the victim looking as nearly alive as possible.
It should be applicable by the Ruquelians who are at a roughly 1930's level of technology.
I forgot until I read the answer about the bolt gun: the heads of the women are returned to their families for interment, so they need to look as good as possible.
While euthanasia of women is both law and tradition and some are willing or even eager, many are reluctant or opposed, so the process must not rely upon total cooperation.
Given these criteria, what is the best way that the Ruquelians can kill people for human consumption?
I have already considered and rejected the use of the guillotine, since historical evidence suggests that it may be less humane than it was originally thought, that on some occasions its victims might retain consciousness for some time, and it would also be emotionally traumatising. This is undesirable for a victim who may reincarnate and remember the experience.
Likewise, I have considered and rejected the use of lethal injection, as the residual lethal substances would leave the victim's flesh unsuitable for consumption, as well as for the lesser factor of risking emotional trauma if improperly administered.