Help Needed on Slicer Settings

[kx79kx79 0]

I need help on the Slicer settings. I am using Cura. I am printing a slender rectangular shape for testing purposes.  I need to have a pre existing crack in my specimen. I am having difficulties generating the pre existing crack in the Slicer. (See attached pictures ). The real specimen shown is some study I found that shows the final product and that's basically how I want my part to look like. I need the printer to generate a very small xy plane where the filaments skip and don't adhere to. Can someone help me?  Also, I am using PLA diameter 1.75 mm and Raise3D N2 printer. I can upload the .stl file if need to.