you have to butt it together, ahndle is best.
Butt (pun intended), if you have to do it mid limb, then lay the one piece down and let it dry. Then sand with a block until you get rid of that square edged "step" from limb back to rawhide. Then lay the other piece down so that it overlaps and allow that one to fully dry, too. Then carefully sand the square edge off until the two bland into each other. It would be much easier than trying to make a scarf joint.