You can use plywood for most of the seat, cut to a curve, leaving only the trim as the tricky part. I have not done such a project but the way the pros do it is by steam bending. I've seen it on DIY programs. You can use a piece of PVC pipe with a cap on one end, stood upright, as a soaking container. Soak the wood in hot water for awhile, then switch to boiling if you have to. Make a form using nails or dowels sticking out of a piece of plywood or OSB. When the wood is soft enough, bend away. Let dry for long time and it will hold its shape. Probably best to do this first and then cut the rest of the seat to fit the curve.

You can probably find this on YouTube, etc.

You could maybe find a veneer that you like for the edge and then add some wood medallions over them. Or you could use a router create the grooves along the edge. Check out a specialty lumber store or a woodworking store and they are always glad to help.

Another option is to find a round table top and cut it half to use as the seat and add legs and upholstery.

I also saw a DIY recently of someone who used a soft wood putty in a squirt tube like thing (like a toothpaste tube) and they applied that in long strips. Let it dry and sand and painted over it. They were going for a bamboo look and it turned out pretty good. Just an option to think about to add detail.

Use this for the trim. Can be painted and stained.

Many options.

https://www.google.com/search?client=firefox-b-1-ab&tbm=isch&q=flex+molding&chips=q:flex+molding,g_1:decorative:r2iTokvfrg8%3D&usg=AI4_-kSbBE_BhgMMd8NW63lhQT-eSyxh0A&sa=X&ved=0ahUKEwjd8eWmv4ngAhUGd98KHQhlCOcQ4lYIJigA&biw=1536&bih=732&dpr=1.25

Use plywood for the half round.

Buy a touch up kit or stain for future maintenance ie: scuffs