You could create prongs on a sturdy base, solder or preferably fusion weld the unit onto the butt of the pommel, then set the gem and fuse a small security ring (L shaped in cross section) onto the area of the prongs near the apex of the bend on the arm itself to hold the gem's girdle....in effect, this is a basket mount. A fancier method of securing the basket would be to create prongs that a re long enough to meet in the middle and turn up..., file them so the ceosssection of each is wedge shaped, clench them together, thread with a tap and die tool, then set a drilled metal ball of softer alloy onto the "screw" and use it as a nut....both methods were actually used on ceremonial blades...rarely were "gems" set into functional blades except on the hilt or sides of the quillions and even then, usually glass gems...ancient Gallic slashing long Blades show this, e.g..
