I remixed erin.wang's rose model to float in a decorative transparent shape. Also a big shout out to ExtremeElementz's How To Print Ice print profile, which was a big help in printing transparent PETG.

After printing the model, I sanded down each side, and then glossed the entire model using a thick spray-on glaze (recommended by OliasOfSunhillow).

Fair warning, this model will take a long time to print, and you may see some scarring on the surface. Most of that can be addressed with the sanding / glossing described above.

I've uploaded the raw model file of the shape I designed, but you would have to manually add the flower to the shape as a modifier.  If you want to make any modifications, it would be easier to start with my print profile.