Making an arc for inside breadbox

[WillAdams (William Adams (Carbide 3D))]

If you wish to do this sort of thing manually, that was shown in:

Oar holder project

have been asked to help with an oar holder project. Here is the part that I would like to use CC to design and then cutout. Using this to learn…much more complex than what i have previously done. Not totally sure how to start. Maybe start with Create Curve and then the note editor??? Just looking for basic direction. tx. [oar holder layout]