Using the flextable package and reading from the different help pages, I could not find how to double (line) space an entire table, as APA requires.

There's the option hrule():

ft_1 <- flextable(head(iris))
ft_1 <- height(ft_1, height = 1, part = "body")
ft_1 <- height(ft_1, height = 1, part = "head")
ft_1 <- hrule(ft_1, rule = "exact", part = "body")
ft_1 <- hrule(ft_1, rule = "exact", part = "head")
ft_1

Or padding():

ft_1 <- flextable(head(iris))
ft_1 <- padding(ft_1, padding = 20, part = "all")
ft_1

But in both cases, when I check in Word, it doesn't correspond to double (line) spacing (it is still single spacing there).

Is there another option to make sure it 100% corresponds to the double line spacing rule ("Line and Paragraph Spacing" in Word)?

I assume that using hrule() or padding could create various formatting problems later on, or editors might complain it doesn't correspond to the right kind of double spacing (e.g., it doesn't respond to changing spacing manually after so its harder to change through conventional means).

Or are we expected to manually change to double spacing in Word manually after exporting?