I haven't stuffed it for the small size yet (waiting on more to be delivered so I can use for both) so I use both inserts for DS.

I put the inserts in, hold the end of it, while bringing my hand down towards the pocket opening so it flatterns by my palm on the way down - if that makes sense?

Bit clueless about the stopper unless they mean the snaps on the bigger insert where you fold it down?