Hi, check out my high poly bishop on which I spent more time than I should have ^^’ :
https://gyazo.com/9329d84cf9c12c6b2921e3203c733f82
And here is the notch I modeled to use with the difference boolean modifier :
https://gyazo.com/980555bc2af4c948fa19c6e58c45b4a3
Btw, I created the notch by making a bezier curve, extruding its mesh and then snapping it to the surface of a cylindre, followed by many slight modifications.