I wanted to create something simple for the Back to school contest. While erasing probably fifth iteration of what I had in mind, I took a closer look at the eraser and this is the result.

Printed in PLA while testing new to me 0.8 nozzle which is not ideal :)

Print in covers in PETG and the tray in PLA. Covers simply slide over the tray.

0.2 layer 

30% infill

Print tray laying flat, no supports needed.

Print covers standing upright with support. Alternatively you can lay them flat on the angled end if you have well dialed in overhangs and they can be printed without any supports.