As I understood it, what goes into leafmould is the kind of leaves that fall off broadleaf trees. That's it. Those are low in nitrogen -- unlike your green spinach leaf -- and if you just pile them in as you rake them up, they'll mulch down into lovely fragrant, loose-textured.... er, brown stuff. Don't put in pine needles or bits from conifers; they take longer to break down and are acidic. If the leaves are still on small branches/twigs, that's fine, as long as you're prepared to pull them out later! (Which is probably faster than stripping the leaves off in the beginning.)

I'd envy your netting box, but my leaves blow away before I could collect them anyway! *wry g*