Wanted to be able to store pens "optimally", and prevaling wisdom is with the tip slightly lower, but closer to flat. So this lets you choose your angle (10 degrees by default), as well as the number of pens it stores. I also gave it some bits so it stacks well, and tried to make it as parameterized as possible.

For some reason OpenSCAD doesn't seem to do rotations quite perfectly, so make sure you force the bottom to be the bottom before printing. You could probably also print back-side down, which would make the holes cleaner, but would take longer and may make it not stack as well or be as rigid (untested).

Printed no brim or supports, but I was okay with a bit of uncleanliness in the pen slots. YMMV may vary based on your printer's ability to deal with arches.