In February 2018 I released a font called Cadman which uses a very neat piece of code for doing arbitrary fractions by Erwin Dennisen the author of Font Creator. It is a bit complex but it works very well.
The original code is given here.
If you don’t feel like tackling anything this complex yet you could just download Cadman and substitute your own glyphs into the appropriate character slots but not alter the open type features (you would have to re-name the font, we can’t have two different Cadmans out there). Of course there might be some things you would need to adjust but you can always get help with that on this forum.
I hope you realise setting up the font to do fractions is just half the job, you also need to enable the fractions open type feature when using the font in a word processor or DTP program. This can be done for just selected sections of text.
Good Luck! 