Turned out this works well - No assembly, almost vase mode
Print only the main part
Perimeter generator: Classic
Spiral vase: No
Layer height: 0.28 mm
First layer height: 0.28 mm
Perimeters: 1
Solid layers top: 6
Solid layers bottom: 6
Seam position: Aligned
Fill gaps: No
Infill: 0%
Extrusion width external perimeters: 0.8 mm
Extrusion width infill: 0.8 mm
Extrusion width solid infill: 0.8 mm
Scale: 100%
Retract on layer change: No
Place the phoneholder with its front facing the part cooling fan
By preventing the aligned seam from being placed as in the image below I managed to trick PrusaSlicer to place the seam inside the model. In combination with not retracting on layer change it is almost vase mode - except for some layers where the printer will move to put some additional filament. Setting infill extrusion widths as above keeps it to a minimum though.


This phone holder is specifically designed to be printed in vase mode using these settings
Spiral vase mode
Perimeter generator: Classic
Layer height: 0.28 mm
First layer height: 0.28 mm
Solid layers bottom: 6
Extrusion width external perimeters: 0.8 mm
Brim: I didn't need it
Scale: 100%
Slicing it differently will most likely not work well.
Successfully sliced it will print as one continous line of plastics after the 6 bottom solid layers.
Place it laying on the side as shown in the pictures. Take note on where the turning point of the spiral extrusion changes from back to front (and further up back again). Toggle the slicer layers (not actual layers in vase mode) and make sure the gap on the other side shows up just after the bridge takes place. See image.

There will be two vertical lines visible in the final print, this is inevitable due to spiral changes direction inbetween cable openings on front and back - when bridging a finished cable opening the extrusion will continue on top of a slightly different height.
The separate part to "press fit" in the side of the model can be printed however you like, keeping the same settings as the main holder will ensure solid print since it is 6 layers high. Some cutting and adjustments to the side part is needed, at least the upper part.
I printed it in PLA on my Prusa Mini+ with volumetric flow ~13 mm3/s (slower for overhangs/bridges) in 1h14m + 7m for the pressfit side.
Modifications to this phone holder is very difficult since there are small gaps in precise places throughout the model.
Hope you like it, have a nice day!
The author marked this model as their own original creation.