Aglais urticae pairings

Hello
my i found a quite huge amount of Aglais urticae in march. I released most of them but I have kept some to try reproduction.
I was wondering if it was possible/easy to obtain spontaneus pairings in a 35x35x60 cage with some nettles inside or is hand pairing is an option.
any recommendations?

Thank you in advance.

Valentin