Want to get even more accurate? Or see how accurate your 3x3 mesh is when printed in a 5x5 mesh?

This is a 5x5 mesh you can use following the original instructions from the original model at the link below and its optimized to work with the Professional firmware which allows you to easily move to, probe and then edit a specific spot in your mesh that is matched to this printable grid.

https://www.printables.com/model/213992-perfect-1st-layers-ender-3-v2-ender-3s1-ender-3s1-

Model includes “fingers” to extend 10mm beyond the probed mesh squares in all directions so you can get an indication of how well the print works outside the probe boundaries.