I decided to make ours out of a box I had saved which was a good size. So we ended up with four compartments, though I'm not sure how change a child saves can be used for investing... I started off with a box that I cut with two pieces that open on the top to get access to the money when needed. I used clear packing tape to keep the sides together as I needed.
Now for the two top flaps I left to open and close to access the money, I decided to use a piece of my daughter's art work for a personalized touch. Again, I cut the paper to size and was able to use just one paper for both flaps. And again, I covered them in clear tape.
Next I took a razor blade and cut four slots in the flaps over each compartment I made. It was much easier and quicker than using scissors, and I trimmed off any excess cardboard with scissors when done.
To keep the two flaps closed, I cut a small but thick piece of cardboard and covered it with another small piece of her artwork left over. I covered in it tape, and then added two pieces of velcro to each side on the bottom. Then I put it in the middle of the box, evenly in the middle of each flap. This way the velcro provides easy access when needed.
And lastly, I took four different colored permanent markers and let my daughter decide which slot would be for which, and then labelled them as such. We spent our afternoon counting money, putting what we could in rolls, and separating it into the different sections. My daughter has such a giving heart so most of it went into the giving slot for her to send to help save wild cheetahs. :)
This is a very simple and reasonably quick project, and it's so much cheaper than buying a pre-made bank, which seem to start at $30 and up! If you make one for your child, let me know how it goes and what you used! :)