Tips and information about using the Prusa Slicer for 3D printing.
Top / Bottom Layers
In Printer Settings / Infill are settings for the kind of fill used on a bottom and top layer. The default setting is Rectilinear which has the printer fill in by lines set across the model layer. However, if you have a round first or last layer you might try Archimedean Chords, which is essentially a spiral; this will give you a smoother finish. Other choices provide a more interesting pattern to the bottom or top layers. Select one of these and look at the rendering in the slicer to give you an idea of what they will do for your model.
This blog from Prusa goes into great detail about the different infill patterns.