I of course dump the measured powder charge down the bore first. I apply a little moose milk to the strip of 100% cotton pillow tick patch material.
I then center the ball on the material dead center. Using the short nose on a ball starter I then drive that ball under the muzzle.
You will now see how I make a perfectly centered patched roundball.
I pull the material together and cut it off above the muzzle. Now you seat that patched ball the rest of the way into the bore with the longer nose of the ball starter and finally with the ramrod to seat it on the powder charge.
When you figure the thickness of your patch material remember you have to double the patch thickness, because it contacts the ball on both sides. So I use a .490 ball for instance. And then 2x .018 which makes .036. That sounds like a lot of patch. .490+.036= .526 but you want the patch to fill the lands and grooves of the bore. Plus as you force it the cotton will have some give to it also. So what I have is a nice tight fitting patch and ball set up.