2 Layer bed level with numbers

You can stop the print after the first layer. The number help identify each block and orientation after taking it off the bed.
Curved lines help to check for material adhesion to bed
Can also be used to check effect of different parameters on first layer. Adjust speed, nozzle temp, bed temp, fan speed while printing each square to check the difference.
Dont forget to note down the settings for each square to help in troubleshooting