Here's the updated version of my Switch Joy-Con holder. I've removed any issues that should prevent it from needing any supports as well as addressed some gaps that confused some slicers. I also slimmed it up a bit, making it a bit more compact / travel friendly.
Essential print settings, make sure that you have at most a .4mm nozzle and set the nozzle size in the settings to .4mm ( default for some is .48 ). layer height and infill shouldn't really matter. No supports needed.