Never worked with G-10 but did do up something like that years ago. I cut out the slot VERY carefully with a Dremel burr that matched the shape of the flint superglued it in and clamped it up with tywraps and cleaned up the excess with acetone . I used super glue so I could replace the flint a few drops of acetone loosens the superglue right up. It turned out so nice a friend copied it but forgot I was a lefty, so the flint end up inside his normal grip area and he turned a comfortable grip into a PITA. Good luck and hope this helps.