So that brought me to thinking I needed to come up with my own idea... and that's when I realized I could use flat discarded packaging and the Tim Holtz gears packaging was perfect. You use the inner insert that holds the gears in place - it is virtually flat, but has just enough depth that it can hold a Lot of watercolor. The circles are large enough that I ended up pouring a lot of paint in them, so it should last a while. Best thing is it's totally refillable. I have the 18-pack of Holbein professional watercolors, and I picked my favorite 12. So I have professional-grade watercolors that will permanently come with my notebook. I insert it into one half of the Midori kraft folder.
If anyone wants an actual video tutorial, let me know, and I will make on for my YouTube channel, and take you though the process of cutting the materials, properly filling the "wells", etc.
And here' a YouTube video to give you a better idea of how it looks: