The paper I use is an old ream of onion-skin typewriter paper. No idea if such paper is still available. It's a little more "brittle" than white printer paper and easier to bite or tear cleanly.
What I do is find or make a dowel of the ball's diameter. A wood dowel with masking tape to bring the diameter up is fine. I have a pattern of cardboard that gives 2-1/2 full rolls around the ball. You may need more paper thickness to get a snug fit depending on your bore/ball marriage. I lay the pattern over 10 sheets or paper or so and cut them out with a razor knife.
Then I roll a paper on the dowel I back it off 1" or so and tuck a ball into the paper tube. Then I wet my fingers and roll the paper tight over the ball. That makes a twisted end - like on a small Tootsie Roll or Smarties candy. With carpet thread I wrap two times over the twisted paper up tight to the ball and tie it off. Then press the ball back in tight with the dowel.
Now, two loops of thread pulled tight up where the ball meets the dowel and tie it off. This just holds the paper tight on the ball and keeps the powder from working down. Pull the dowel out and you have the powder chamber ready.
Now is the time for fancy option #1: Make a waxed paper insert for the powder to keep it dry when hunting and keep any lube from leaching into it. I do this for my hunting squibbs.
Before adding the powder melt a bit of beeswax in a double boiler (I use a pair of vegetable cans). Big one to boil water in and the little one set in it to hold the beeswax. Dip JUST THE BALL part of the cartridge in the wax and allow to cool.
When cool add the powder (measure and tip in) and then flatten the paper tube, fold the two outer flat edges in and crease them, then fold the flat part down in two equal folds. If you go up to the first image up top you can see the finished squibbs. These are authentic (except the waxed paper) to the British style paper cartridge that goes back to the 1740's through as far as round balls were used in muskets.
To load and fire - grasp your cartridge, tear off the folded end, pour the powder in, flip the cartridge over and start the ball, tear the excess paper away (optional) and ram the ball down so that the beeswaxed paper forms a patch around the ball. When I had my Bess I would prime with the cartridge before pouring (BAD PRACTICE BUT AS DONE IN THE DAY) and I could get five aimed shots off in a minute
Three at 60 yards using my 16 bore Brooks fowler (no rear sight) in a familiar household item found in the woods. That's my max deer-hunting distance with a sightless smoothbore. I use 75gr FFg and a 0.648" ball.
And here's an American cartridge from the Revolutionary War.
Here's a "French" variation with glue instead of thread.
The shot cups I make out of grocery bag paper.