Snipping along the 2" and 3" score lines to the vertical score lines along each edge results in this:
I used double sided adhesive to attach create this box.
To make the pot or cauldron shape, I began with a 2.75" circle, one for each side of the pot. The yellow paper shown below is punched from Stampin' Up's Word Window. I liked that shape for the lip of the pot, but obviously that wasn't going to be long enough. I used that shape to make the black template above it. Two of those were cut for each pot.
I trimmed off one edge of the circle to make the bottom of the pot, then cut a second circle to match.
For the next step, I placed one box on the circle with the cut off bottom and drew a pencil line to show me where to cut off the top of the circle. This is easier to do before you attach the circles to the box.
This might not be necessary, but in an attempt to keep the sides looking alike, I marked which end would be up on these lopped off circles before adding adhesive and gluing them in place.
The top edges of the pots were also attached with tape runner.
I had originally planned to use Copic Markers but didn't have a red that I liked for the rainbow. I used Tombow markers instead, the color numbers seen below. For a little extra body, I backed the rainbows with black paper before inserting them into the pots.
Here are twelve pots of gold ready for the birthday girl's party.
This is a 6" single-layer cake that will be the birthday girl's to daintily eat or destroy, whatever she wishes.
Time to get the party started!