I read 3 different methods on splicing and 2 of them were like brain surgery to me. The third one basically said to measure, cut and attach and for me that worked.
One thing I found is that in the mating areas, the barbs(hairy things) have to be the same size and stiffness for the splice to come out right. I found I could get one forward piece(longer piece) from a full length feather and 3, 1" back pieces from one full length feather. I was using a 5 1/2" high profile shield cut with a 1" splice at the rear. That is the only type of splice I did. Basically I would measure the front section and cut it out, then measure the rear piece and cut it out. Then I put the two together. If the pieces match well enough the barbs from both pieces would mate and hold the splice together. I clamped it in the fletching clamp, added glue like usual and attached it to the shaft.