i learned knapping as a child from my mothers brother, my uncle. when i got into flintlocks i just naturally made my own flints.
I also learned to make BP when my brother gave me a Springfield trapdoor for Christmas so i would stop swiping his m1 carbine to hunt .
with the rifle he gave me tools to reload and the ingredients that when combined made gunpowder. have never needed to buy any from then on. i have had people give me gunpowder with a gun i bought from them. Hercules, Dupont, and Goex among others. i used the commercial stuff as a control if you will when making my own. hope this explains.
my dwindling supply of flints. need to make some more.
a chert knife made a few years ago. not sure my hands could do it today.