50cal.cliff
I'm sure others here on the forum could tell you much better than me how to make a ball bag.
There may be a tutorial somewhere on this forum but I never found one.
I'll be happy to tell you how I did it though. I wanted a stiff bag so I used fairly thick leather, about like you would use for a pistol holster. I sewed it flat, then I put it in warm water in the sink, weighted it down, and left it there for 3 or 4 hours.
Then I took a 1/4 inch dowel and forced the small end open, then a bigger dowel until it was the size opening I wanted, for me it needed to be big enough for a 54 cal ball.
Then I got some dry sand and started pouring small amounts in the top and pushing it down and adding more sand and packing it down tight until the leather expanded as far as I figured it would go.
Once all the sand was in I put the dowel back in the top so it would hold it's shape and let it dry for 5 hours.
Then I dumped the sand out. I put several balls in and shook the bag to get all the sand out.
Actually, I was amazed how much the leather expanded, and how hard the leather was when it dried out.
All that's left is carving a stopper.
Hope this helps you out a bit.