One thing I am concerning about ordering PCB is minimum quantity is usually 5 but I only need 1 clock, and remaining 4 boards will be unused.

So I tried to reduce unused boards by creating 2 in 1 PCB.
Since this clock is rectangular box, each opposite panel has same dimensions and I combined each opposite pair of panels to single panel.
This theoretically reduces unused materials by roughly 60% when measured by area.

I also made the MCU board as minimal and exposed as many pins as possible so that the board possibly be used for future projects.

Well, in the rea world, PCB manufacturer send me 8 wrong thickness boards and 8 correctly remade boards.
Now I have 14 unused PCBs. lol