This is a simple wall clock I made to be displayed. It is 170mm in diameter and 23mm thick.

In order to save material and time, I oriented the clock to have the numbers facing down on the print bed, then set the top layers = 0 so that the infill shows on the back. You can mess around with the infill to find the right look for you. I used about 13% infill, grid design.

I also oriented the infill so that the grid design will hang the clock perfectly in the center when putting it onto a wall. This took away the need to put a hole into the design.

I bought the clock movement in a four pack for $15 from Hobby Lobby (see URL at bottom) but any crafts store should have a one that fits. The hole in the back for the movement is 56mm by 58mm.

https://www.hobbylobby.com/Crafts-Hobbies/Wood-Crafting/Clock-Making/Mini-Quartz-Clock-Movement-Value-Pack---1-4/p/29759