You can cut a Z splice with a hand saw, it doesn't have to be perfect.
Draw your pattern on a piece of paper first, glue it on your limbs lining it up with the center line on each billet. The picture is of a limb replacement with splices layed out using a a pattern.
Cut just outside the lines the best you can, then your heat splices really hot with a heat gun, fit them together and clamp with three C clamps then let them cool before you glue them together. The splices will bend and conform to each other and you will have a pretty good fitting splice.