I accomplish mine using a crusting buttercream, hot-knifing and then a cloth with a fondant smoother similar to the paper towel method.
When you have a really good crusting buttercream it is very easy. It can be done without it, I'm just talking what's easier for me.
You can do this without the hot knifing method, it's just 4x faster with it.
Anyway, after smoothing my cake using a hot knife, I lay my cloth over the cake. It should hang over the edges. I then use my fondant smoother and shape my edges.
I don't like many borders on cakes. I think it's too busy, especially on a smaller cake. So I had to learn or be unhappy with my cakes.
Here are a few examples:
(I messed up the left side border after finishing the cake, but look at the rest of it)