"It is a very well guarded case. I make sure I take very good care of all of those briefings because there's lots of information we need to be careful with."
It includes Cabinet papers and Cabinet committee documents that she needs to be across before Cabinet meets on Mondays.
"[I] still try and get out and about as well [in the weekend], to community events whilst cramming in a bit of reading in between, and that will be the same for all ministers. They all each have their individual readings that we send to them on weekends to make sure they're prepared for the week ahead."
Ardern answers live messages during the video, saying at one point: "I promise I will never leave it on the roof of my car, thank you Robin for that."
She also gives a "kia ora" to her cousin Crystal, adding that "we can still speak on the phone. We don't have to communicate via Facebook Live."
And: "I look tired - thanks Joseph. No, actually, it's just that I don't have much make-up on. Thanks though."
She then gives a plug for her efforts to improve Government transparency - an issue over which she has been under scrutiny.
"There are papers in this case that are decisions we're going to make. One of the things we're doing a bit of work on now, in conjunction with the State Services Commission, is how we can make sure we are sharing the background briefings and Cabinet papers that we've read that have lead to a decision we've made, and how we can do that on a regular basis so people have access.
"We're doing work on that now so we can improve transparency around that decision-making whilst at the same time making sure that we still get really free and frank advice from our public servants.
"What we don't want to stop is them really telling us how it is."
The video has been viewed 72,000 times by 9.50am this morning, with over 1500 comments.
Ardern starts the video saying she hopes no one is full of the work dread "that usually happens on a Sunday night" and finishes by thanking people for tuning in.
"When I next think of something that I think might be interesting to you other than my little black briefcase, I'll share it with you."