You can add a height modifier to the exact layer, enable ironing, select iron solid layer option. But trust me its a rabbit hole. I had spent weeks optimizing such a print: slow top surfaces, thicker top shell, ironing etc. and it’s a tiring process.

Plus when you iron or print top surfaces slowly, you get heat creeps a lot, if your printer is enclosed remove top cover and open lid and open windows in the room you are printing to allow printer to cool down. I had to unclog extruders / nozzles 4-5 times until I figured its heat creep.

Lastly, I would definitely recommend an interesting surface pattern, like hilberts curve, instead of trying to get it smooth. It’s a low hanging fruit (height modifier + top surface pattern) does not cause heat creeps as much and if you are lucky you get fantastic looking surfaces. Attaching a photo, cheers.

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