This is a quick test to determine if your first layer is set up to be the right thickness for printers that do not have an auto-leveling feature. I have used this often for my Ender 3 Pro whenever changing the bed or nozzle to refine the offset after doing the paper/shim alignment.

I have build files for the Ender 3 Pro provided, so the geometry is designed for a 250 mm build volume with a single layer of part. If your printer has a different bed area or layer thickness, please scale your parts in X/Y to fit the bed near the corners. Additionally, you will need to use whichever settings you plan to use for your parts, and scale the Z dimension to match your layer thickness. It is currently set up for a 0.28 mm layer.

When you complete your print, label each circle before you remove it from the bed. When you remove the parts, you can quickly tell if your layer thickness is too thin or thick by touch (see attached image). If your layer is too thick, it will extrude separate rasters that you can pull apart with little effort. If it is too thin, your nozzle will over-extrude and you will feel a rough texture on the discs. Your thickness will be in the acceptable range when the disc is hard to separate along the raster paths, and has a smooth texture.

If you want to be more precise for your layer thickness, or need to calculate the zero-offset for a bed leveling system (such as on the LulzBot), you can measure the thickness of each pad with calipers and adjust your zero offset from that measurement.