I recently got some 45g and 75g lead glande that are similar in size and shape to old Roman glande that had been found. The slings I have have bigger pouches (balearic, leather pouch, smiling slim sling) and I would love to get my hands on  a sling that the Romans would have used that this type of ammo was made for.

Joe summed it up really well. I would however like to highlight the point he made about the Roman military taking on slingers of many cultures - we are never, to the best of my limited knowledge, told about a standardized sling being a part of Roman soldier kit. We know so much about the standard ancient Roman soldier kit, but a sling is never mentioned except as being a weapon useful to soldiers. And look at all of us here - we're a weird mismatched bunch of slingers, each with our own preferences. I love short and chunky Balearic style slings to lob stones of about a libra in weight, but there are slingers that use long noodly slings and quail egg sized stones. I'm no better or worse for using such a sling, and I'm sure we'd be formidable if all of us were put together - at least one of us would be bound to hit an enemy 

So much of slinging boils down to preference, and I'm sure that's been the case for millennia. Different fibers, different styles, different grips, different weights, and even different stone/bullet size preferences. I don't doubt that the slings used to throw the ~45g lead bullets of antiquity would be very different from the slings used to lob stones weighing a libra. And even then, I would say that in whatever Roman-occupied region the soldiers were recruited from, they would likely use the slings they were familiar with, and modify them or otherwise to make them work with the ubiquitous sling bullets of that era. So, in summary: a Roman soldier could perhaps have seen and/or used styles of slings like yours 

there are also the egyptian slings but I would say they were made for close range or for rapid use on chariot. I don't think the romans would prefer woven pouch over leather pouch or split pouch

I haven't used rawhide but the earliest modern range record is with big rocks and rawhide lacings 29"
https://news.google.com/newspapers?nid=336&dat=19720419&id=XsdYAAAAIBAJ&sjid=9H0...

xud9a - call me zud 👍 wrote on May 8^th, 2025 at 4:54am:

Good call out.  I don't think I've seen that before.  I found some discussion on here about that from a while back: https://slinging.org/forum/YaBB.pl?num=1252088442.

https://slinging.org/forum/YaBB.pl?num=1361973151/0
I was inspired from this to make leather pouches when I started messing with leather years ago.
check the pouch dimensions, these would be for small stones or for lead.
Although I havent done a lot of lead slinging I think split pouch with sewn leather pouch might be better than a split pouch or a plain leather pouch
PS: dates aren't bad either

After alot of studying I think the best sling for this type of ammo (Lead Glande) would be what people call an "Apache sling" I've made my own with hemp and kangaroo leather. But I my next experiment will be to make it out of sinew and kangaroo leather.

The Romans had a 5 tier system for their army. Slingers, along with archers and javelins, were the lowest. This is because they did not face their enemy directly
  They were  called Numerii, or auxiliary. Informal companies, mad mostly of volunteers and prisoners who decided to join. They had no armor other than a small buckler.
They would act as a unit, all using the same underhand launch and all launching at the same time. Presumably the slings would all be the same as well.They would be used in an opening volley, then retreat to the sidelines and pick people off, sniper style.

What you're saying isn't correct. If slingers were at the lowest level, why do they bear legionary stamps? A Roman battlefield was excavated in Switzerland. It had many glanders. They bear different legionary stamps. Arte did a good documentary on this. The fulminata was an elite unit and very feared. Your underhand theory is also untenable. The battlefield in Switzerland clearly proves this. There was very targeted shooting. In very mountainous terrain. Not possible with underhand. I was there and shot there.