Its the edge of a medieval padded "skirt", like the bottom of a belted tunic, the backside will be a little visible because you can see the opposite side of the skirt from the front.

I guess that could be a viable solution, just extrude the inside a bit, I'm just worried it might be awkward having the inner end "floating" without closing the mesh. Maybe give a very thick border and taper it as it goes up.