always load ammo horizontal to the pouch.
unless it's spherical
Most common way to hold a sling is with the retention loop over your middle finger with the cord pointing up (ie: above the back of your hand).
The release cord us then gripped between your thumb and index finger. Or if you have along tail for cracking it runs along your palm. You still secure it with your thumb.
Hang on I'll take a pic
Okay this is the standard balearic grip. It's not what i usually use - but it's a great grip for beginners as it naturally seperates the two cords, reducing the chance of tangling and giving a consistent release point.
I will use it for balearic slings - but not for my own.