If you have ideas, you could try making a rough sketch. Either on a free base, or just an attempt at a drawing. It doesn’t have to be good at all, the goal is just to get your ideas on paper. A written description can also work, but I would recommend a drawing. Both could also work. And if you struggle with choosing between some options for details, my recommendation is to just pick one at random. You will get used to it once the design is done.

Then, you can use your rough sketches and such to commission an artist to make you a proper reference sheet.

This is how I did it back when I designed my sona. But others might have other suggestions

When I first came upon furry fandom I had some drawing experience, but even then it took me good two years to fledged out a design I liked. My first character was a Dutch Angel Dragon but it never felt like sona, but I still use its name “Kaelygon” in most places. It took quite a few character concepts until I ended up with my current one.

So you don’t have to have a sona right now, if you have hard deciding give it some time, explore other’s art and so on. I had general idea what features I liked and that I wanted it to be a simple design but putting all of those together took quite some time. Here’s an imgur album of the character Tiena progression: https://imgur.com/a/HgYIiX1

I am happy that I took my time playing with various concepts, so far I have only changed the feet to more dragon like from the original design and it really feels like a character that I has stuck around with me all of these years.

Pick a cool lookin animal and just sketch until it looks cool for you

If you have a general idea you could send it to me and I’ll try to create an AI art in Stable Diffusion. I can create it in realistic and Anime style. 2.5D CGI could work too but I haven’t done much yet. NSFW optional ;)