An update to my previous model:
https://makerworld.com/en/models/125980#profileId-136156
After the glue failed to hold and the holder - including the hair dryer - fell down in the middle of the night, I decided to design a model using screws. However, it was important to me that the design remains simple and the screws stay hidden. With this model, I present the finished result.
I printed it with 0.16 mm layer height to ensure there are no issues with sliding. However, my draft with a 0.2 mm layer height also worked very well.
Use 2x 3mm flat head screws with a 6mm head diameter to ensure the slider mount works properly.