How to make a vertical font

[Ahzoh]

So I'm making a vertical writing system for my conlang but I'm not sure how to format the font so that it makes the letters vertical like Mongolian.

[Bhikkhu Pesala]

See Font Properties, Metrics.

I suspect that your glyphs will also need to be in a character set used by Vertical fonts.

[Ahzoh]

I was hoping that I would not have to assign the glyphs to Mongolian codepoints to make it vertical.