I use this simple file to test my nozzle height. It is only .50mm tall so does not take long to print.
I check the bottom of the print to see if I am getting good contact and appropriate squish on the first layer.
The exact perimeters and fill are not too important as this is so small. I used 3 walls and 25% fill.
I recommend using a 2 perimeter brim that is offset 10mm to give you something else to compare with.
When I was just getting started I wish someone had shown me a diagram like the one I use for this design. I did not know what a good or bad first layer looked like or how to diagnose what was going wrong. Some prints wouldn’t stick and some were nearly impossible to remove.
Now you know what a happy first layer height should look like. ;)