Stands for cheap and very common insert hygrometers.
The original design is by Leo Visser, called Hygrometer stand. This here is a completely redrawn version with the following changes:
The first layer is crucial since it will be the visible front → keep it slow.
To create the cut out and notches for the hygrometer, a negative volume modifier is used. By default two horizontal cut outs are created, simply rotate the modifier to have it suit your particular hygrometer.
The color change is driven via a modifier which lets you pick different bezel color schemes with ease.
Once printed simply press the hygrometer in place at the notches then rotate it to your desired angle.
The exact hygrometers I used are these but there are lots of similar (and cheaper) ones out there - if the fit isn't perfect for yours, scaling the cut out modifier or entire design will very likely help and not be noticeable.
There may be improvements and modifications based on feedback given here.
I also made a stand for square hygrometers:
Maybe, take a look at my other designs ;-)