You’ve said already that your laser does not have homing or limit switches, which means the laser has no idea where it is until you tell it, and it won’t be terribly repeatable - no grid that you lay down will be very accurate, because you don’t have any way of accurately zeroing the machine itself.
Toward the end of this post is a heading “Homing and workspace” - read this to help you understand how to get reasonable positioning without them: