We used this website to get started with 3d modeling:

https://all3dp.com/2/onshape-tutorial-how-to-use-onshape/ 

We discussed whether to use a continuous servo vs a regular servo and whether to use a potentiometer vs a slider. We are using a continuous servo and a potentiometer in the prototype.

We completed our 3d model of the 3d box and the servo attachments. The code was sent to the printer. The 1st model (in blue) above is the pointer and servo platform. The 2nd model (in red) above is where the servo turns the gear for pointer movement.

One of the problems we encountered during our design process was with the potentiometer. The potentiometer has controlled speed but will never completely stop.