Was z-level calibration done correctly?
The first later is the other side!
If you want to make a good first layer picture, print only one layer, and make a picture.
The first layer should have no holes and stick good together.
If you're using the built-in first layer calibration method, do yourself a favor and ditch it in lieu of this: https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/.
This method makes it a lot easier to gauge the quality of your live z. Feel free to post pictures of your test square for critique. From the picture above it's hard to assess; if you print more than one layer, the next layer(s) will fill in gaps in the lower layer. Also, not sure what those black dots are. Are these holes or debris?
I will check this method. It seems to be very small holes (I can hardly feel it when I use my prints - the sensitive part of finger - to feel it)