This is what the
FAQ and the description when entering the slice of life area says:
"Slice of Life is for roleplays that center around day-to-day lives of characters and more light-hearted stories."
While it's far from normal for slice of life to have magic or fantasy or to be put in another time period, it's still possible elements to have without the main genre changing.
Wolf children is a good, if not perfect, example of a slice of life movie with fantasy elements.
If we go to google and ask for the definition of slice of life we'll get this:
"A realistic representation of everyday experience in a film, play, or book."
If following that definition, then magic or fantasy doesn't have much of a play in things, but historical would still be a good to go subject as long as it depicts their everyday life with a realistic representation.
So it all depends on which definition you'll go with. Iwaku seems to be in favor of the anime version of slice of life, or at the very least they don't have a rule against it as no words in the description says 'realistic' or 'modern day' etc. So putting a certain amount of magic or fantasy in them, as long as you understand where the focus must lay, wouldn't be such a big of a deal.
