Print initial layer only on outside of print
The solution to getting the brim set up was to select the area for each individual piece (in GIMP), then duplicate that selection and "grow" it to make it larger to create the lip. From there, I extruded the larger section a few millimeters and extruded the smaller selection on top of that and hollowed it out. Still working on the exact measurements to achieve the lip width and height, but the process is in place.