This is a small test piece I made to use when playing about with support settings. I don't want to print a large item, only to find my supports are no good. I originally printed out a part with counterbores & when I came to remove the support material, it was fused to the part.

This part is fairly compact 35 x 30 x 12 (Z) and printed in around an hour at 0.2mm layer height for me. It has a standard clearance counterbore for an M6 cap head, a flat roof section (6mm from the bed), a 45 degree overhang & radiused curve with increasing overhang. I decided that these are most of the scenarios I would likely encounter where support would be necessary.

Obviously, you will need to rotate this part in your slicer so the flat 'top' is the top piece of your print & the void features that require support will be against the print bed.

If you use this & find it useful, please upload a pic using 'I Made One' to show how your supports come out. Thanks.