Simple print to live-calibrate Z-offset.

At least in Prusaslicer, this prints such that each line is drawn first, then the square for each line is filled in, in succession. 

This is drawn at a 0.1mm layer height. In Prusaslicer this works fine for 0.1mm and 0.2mm first layer height. For 0.3mm, scale Z to 0.3mm, etc. 

Aside from that, you will probably want to print your perimeters very slowly, this gives you more time to adjust.