I threw away the leather and pounded a round ball flat and used that to wrap the flint.
It held the flint FAR more securely than the leather ever could have hoped to.
Go to a gunshow and see if you can find any English Chert knapped flints. The sawn flints that you can buy are, in my experience, absolute crap. I normally could get no more than 20 or so shots out of a sawn flint.
I could easily double that with English Chert.
Also, the brass ferrule on your short starter (if it has one) makes a dandy flint knapper for quickly sharpening your flint. No need for a small hammer and weird screw. Just learn it through trial and error how to strike and how hard to strike.