This is how you can print squiggly lines with flat print:
Make wave form to the side of the object and print it in 45 degree.

I used Prusa Mini+ with PLA & 0,20mm layer height.

WARNING FOR SINGLE FILAMENT USERS: 
1. More lines = Better looking mirage.
2. More lines = More filament changes.
3. More lines = Shorter filament change time.
4. Mire lines = Longer printing time.
…I have only Prusa Mini+ and I hope to get Prusa XL some day, so printing these would be easy. But other hand, then I could just print wiggly lines without miracles, planning and puzzle solving…