Well welcome to everyone's path to making call inserts. It took lots of practice for me to understand and also turn out a good insert. Your question is quite generic in content. Things that effect the sound of a duck call hmmmm 🤔. Hole size, tone board height, Reed material, length of the tone board hole in relationship to the back of the cork notch, size of cork notch, length of cork notch, upslope vs down slope, material of the tone board, and believe it or not the length of the barrel of the call. I'm sure there are more things I'm forgetting but these are the ones that come to mind. Can you narrow it down a bit?
Larry