I used this "Thing" to make a nice enclosure for some sonoffs I had:

https://www.thingiverse.com/thing:2982177

With the Sonoff Basic R2 that I got, the toggle button on the sonoff was shorter than how the switch was designed. I made a little topper for the toggle that you can affix to the top. You can put it on after the sonoff has been slipped inside the box. You don't need to glue it either. it will be trapped between the toggle and the switch anyway. Besides this way you can take it off easily should you need to get the sonoff out of the enclosure for some reason.

I printed this with the taper side down to make sure the length of the hole down the middle was as accurate as possible.

If there are other sizes required, let me know. The filename indicates the length of the gap between the sonoff toggle switch rod and the bottom of the switch pad. Mine was 1.75mm different.