Well, I’ll bite on this. I take my vernier calipers and measure the width (front to back) of the TOP of the sight base, and the depth of the sight base. I then Know how wide ( front to back) and how deep the dovetail should be. I mark (scribe) these on the barrel ( depth of cut will be approximate...be conservative.). Then using a hacksaw I kerf between the marks to depth, both at right angles and diagonally to remove as much material as possible. Control the depth by counting your saw strokes...makes for uniformity. Clean up with a file with safe edges. I clean out the angled ends by using a jewelers saw to put a horizontal kerf across both ends, then use a safe edged triangular file to finish ( 2 safe edges on this file so you only cut one surface at a time. Make your slot VERY slightly tapered to ease the entry of the sight base. This allows you to have a good fit without damaging a soft copper base. Be careful and keep trying and fitting and it will come out nice.
Mikeyfirelock...Hoosier hammergunsmith