I first checked online, as a box shape would be such a common in the origami world, but found that mostly equilaterals, which were hard to modify, but I did have some success:
https://www.youtube.com/watch?v=d9Zg8w4-px4
The first half of this I managed to modify to this:
![Image](https://i.postimg.cc/qtmzS06T/mod1b.png)
![Image](https://i.postimg.cc/K1DK7tZ4/mod1a.png)
Then I found the following: https://www.youtube.com/watch?v=caDwbe02l6g
Of which I was able to shrink the size to, but not get the length:
![Image](https://i.postimg.cc/5XycpVJv/mod2.jpg)
I need something that will cover the entire length of the pocket tissues (10.5cm x 5.5cm x 2.5cm), with just a little room for pinching at the top (to remove a tissue) and of course an open top.