I've modified this tray for adapt the both parts to my Prusa MK3 print surface.
I've used Slic3r Prusa Edition v1.41.0+win64 for slize both parts. The profiles used are the default Prusa PETG.
How to merge both parts?
I've put some Super Glue along all the union side in one part. Next, put the other part aligned in a flat surface. Finally, use sodium bicarbonate for consolidate the union.