I own a lot of scarves which I don't wear enough but have such lovely fabric.
There are no before pictures but I think you can work out what I did with this viscose scarf and cotton t-shirt.
This is the rather messy inside of the t-shirt where I sewed the scarf corner on, but did not cut away all of the t-shirt fabric. This helps with the stability of the thing. I left the back of the t-shirt as it was.
I'm going to use this method again, but the scarves fray a lot and some don't wash well and some are vintage so it would be wrong to cut them up. So guess what I've done, yep I've bought some extra ones.
It was also quite fiddly to get the points of the arms and shoulders exactly in the middle, but I was and still am, pleased with the result.