A simple way to mount a SPDT miniature toggle switch for your project. You will need 2x M3.5 countersunk screws, M3 also works.

I use this to turn on off LED strip mostly.

Please note,  don't use this tiny switch to control AC mains although it is capable of switching 240AC voltage. It is best to switch 12V DC or so, instead of switching AC mains voltage. Use a beefy proper switch to turn on/off AC mains, like this one

Working with AC mains IS VERY DANGEROUS. You are warned.