Hello Paean Perplexed and welcome.
Interesting knotting need indeed.
I would probably take the easy road with a sack or net of some sort, tied at the top with a sack knot of which there are many. Even a bottle sling knot will do. I would choose one that tied and untied easily and that would have enough left over to either attach to a belt, pack or to make a sling/handle with.
Now for strictly using cord, that is another story. I would make a ring (3 or 4 rounds) of the cord approx. one half the major diameter, then half hitch around the ring to unify them, after which I would lace the remaining cord through the ring or half hitches leaving long ,equal bights to form the attachment or handle.
Uses quite a bit of cord mind you.
Just an idea.
SS