I might put the slabs of my choice on and then fill that bottom area in with acraglass epoxy colored black. You could fix a dam around it and pour in in ,one side at a time. You want the epoxy warm and thin to reduce bubbles and slowly pour it from one side so you won't have any voids.
It looks like that pommel is pinned on. I might do away with that all together. I would like to see what an original looked like and possibly remake it.
