Sorry...my bottle just has a resealable pull-up cap, like those on some water bottles. There's no filler tube or means that I can see to get it into the box. And I was concerned as thick as it is, that it won't readily flow into all areas and displace the air in the box as I try to fill it.
I'll try a few things, but I do assume that it will "flow" over time and I'll need to check and top off a few times after the initial fill.
Thanks