I think the most important thing it to choose a day when you have lots and lots of time.
I always think it is good to leave them in the bonding pen for as long a possible, so you can not only see how they react when they wake up from a nap, but also when there is a sudden loud noise in the distance, or a bird tweets, or you put the coffee machine on, or....
Once you start you have to be prepared to sit it out, and do it on their time, not yours.
Make yourself a coffee, grab a good book and be prepared to hang around for a while.
When I first bonded my 4 (I had 3 and added another) I left them in the pen almost all day (around 7 hours).
When they seemed settled I moved them into their new cage, but then did not handle them or change anything much for a further 3 or 4 days. I wanted to give them every chance to settle in together without interruption (apart from topping up hay, pellets, water, etc).
In all honesty I would say it was probably just over a week before I felt they finally settled and everyone had agreed on the pecking order.