USB tiny ISP box enclosure

Simple box, no glue, no screw needed, just slide the board inside.
Print it at 45 deg angle (see screenshot), and add support under it (partially or fully) to improve the rigidity. Maybe you can print it with a large brim and no support as well in that position, but the contact area with the building surface will be very small.
No support needed inside.
infill probably not needed, I went 2 perimeters and 100% lines infill though.

2 models : one with, and one without the text (VCC & GND).

PETG worked very well for me.
0.3 Nozzle is good (this is quite small), wall thickness is 1.2 mm.
For a 0.3mm noozle, I recommend external perimeter 0.25mm(for good precision), internal perimeter & infill 0.65mm (for strong layers bonding).
0.4 Noozle should work as well.