I started with a picture and made it black and white. Using Cura, I imported the picture making the darker areas higher (don't recall the measurements, but this was a lot of trial and error). Once I had the 3d image looking reasonable, I mirrored it and placed them side-by-side, then sliced. Using that gcode, I imported it into Voxelizer. After voxelizing it, I re-exported as an stl. The resulting file had a ton of errors and missing/duplicate faces. But I think I cleared them all up.