How to make a perfect z offset ?

do an ‘auto-level’ of the table and determine the z offset.

To do this, take FirstLayerCalibration.stl

https://www.makeronline.com/en/model/FirstLayerCalibration/158269.html

(place the model to be printed on the table in the slicer in such a way that the lines would run strictly parallel to its short side.

Then run the file for printing, and increase z offset by 0.05 for each separation, Manually during printing.

At the end of printing, select the best value for z offset.