I have a Prusa i3 MK2S printer. I chose the build your own option to save a bit of money and get to know the printer a bit better. It was worthwhile and the user comments in the online build manual were invaluable.
Like all CAD packages, FreeCAD has a bit of a learning curve. My go-to resource is this excellent tutorial which covers everything I need to create a basic part.
Engraving or creating raised text on a design is very common. The standard tutorial is here which I found a bit complex. However, at the end of the tutorial, there is a reference to this thread which talks about binding a 2D draft object to a surface. Go with the flat face option and when extruding and choose reference rather than one of the copy options.
Once you’ve created your design in FreeCAD, select all the items that make up the shape you’d like to print. This can be multiple Body objects as well as wireframe STL shapes that have been imported for modification.
Using the File pulldown menu, select Export.. as an STL file.
Import the STL file into the slicer program. Adjust the desired print resolution and fill settings.
Export from the slicer as a GCODE file and copy that file to the printer’s SD card.
When printing overhangs, select Everywhere from the Supports pulldown menu. Some shapes can print ok without supports but others really need them. The default support angle is 55 degrees but it seems like I can go as low as 25-30 degrees (went as low as 22.5 degrees with 0.35mm resolution on one print) and it will print ok.